The following data was lifted from John Prebble's book "Culloden", Forbes MacGregor's book "Clan Gregor" and other historical records of the last Jacobite Rebellion of 1745-46.

Describing the formation of Jacobite troops before Culloden: 

Lord George Murray commanded the right wing of the first line.  They came from the Glens and Braes of Lord George's own country.  There wee some 5 or 6 hundred of them from the small clans of Atholl, Robertsons, Menzies, Murrays, and MacGregors, who were not away elsewhere with their Chief Glengyle. They were a puzzle, so many reluctant and melancholy heroes, who might have run expectedly at the first volley, but who stayed and charged with extraordinary fury.

After the battle, MacGregors alone retained a martial spirit:

The last body of Rebels to retain anything like military formation had disbanded themselves as a field force, by the beginning of May.  These were the MacGregors, the turbulent men from Glenstrae, Glenlyon and Glengyle.  'S Rioghal mo dhream! they said, but to the rest of Scotland they were a tribe of thieves and as a punishment for their behaviour, the name of their clan had been proscribed long ago.

Many of them had come out for the Prince because thereby, at least, a man might call himself MacGregor again.  They had been in Sutherland when the battle was fought, chasing Campbells, but they would not take to the hills yet.

They marched home to the Braes with their pipes playing, their broadswords drawn, and the pine-sprig badge of Clan Gregor in their bonnets.  They marched by Stratherrick to Ruthven, by Garvamore, Rannoch and Glenlyon, past Finlarig Castle where John Campbell of Glenorchy, having twelve men only, thought it wiser not to dispute their passage.  And thus they came to their homes.  Or what had once been their homes, for the Hanoverian troops had been there with the torch.  "Every man to his own house, " lamented their bard, "and did not know where it was".

Lord Glenorchy, the anglicized Christ Church Highlander, wished he could have stopped the MacGregors.  In his correspondence with Col. Joseph Yorke, he expressed sour mortification that MacGregors should still cock a snoot at God, King and the Campbells.  "They ought to be extirpated from thence, being the most pernicious race of mankind in being."  Having no roof-poles under which to bide, they lived in corries on the Braes of Balquhidder, raiding and robbing as their fathers had done under Rob Roy.  

"They continue still in a martial appearance," complained Glenorchy, "carrying arms wherever they go and wearing white cockades.  They don't keep in a body, but can assemble 200 and 300 men in a very little time and talk of going to Lochaber."

Note: Some of the Jacobite Chiefs, had tried to reassemble their forces at Lochaber for a resurgent effort but reality forced them to forsake the idea.

MacGregors remain defiant and have their homes burnt:

Alone among the Jacobite clans, the MacGregors attempted to strike a balance, following their old ways by stealing the cattle of some Whig land-owners and levying black-mail upon others.

Glenorchy's Campbells were unable, or unwilling to do much to stop this, so Brigadier Mordaunt marched to Balquhidder with seven hundred infantrymen. Clan Gregor men faded into the hills before him, but he burnt Glengyle's and every house of every MacGregor, and he drove off every four-legged animal that he found.

It was reported Ranald, Rob Roy's son, advised the women not to retaliate in any way or they were liable to suffer the fate of their clans folk in the Fort Augustus area.  the great Scottish poet, Smollett, graphically depicted this slaughter of the innocents in his poem "The Tears of Scotland".

In this way, Ranald, prevented a "Massacre of Balquhidder".

Prisoners escaping:

Not all the prisoners were content to wait for whatever punishment the Government might decide they deserved.  Forty-five of fifty-eight successful escapes were from prisons in Scotland, where conditions were easier and the jails frequently no more than inadequate decaying castles, like that of Dunbarton, from which nine MacGregors hacked their way from one night.

Major James Mohr MacGregor was arrested for his part in his brother Robin Og's abduction of Jean Key of Edinburgh in 1750.  May, his daughter, dressed herself as a cobbler and was admitted to his cell.  After a quick change of clothes, James escaped and eventually reached France, where he died peacefully in 1789.

The burning of Inversnaid and its reconstruction under then Major James Wolfe:

After the Jacobite rebellion of 1715, a sting of forts were installed across the throat of the Highlands from Stirling westward to the shores of Loch Linnhe.  The principle fort was at  Inversnaid, where Loch Lomond poked a finger into MacGregor country.  Its purpose was to keep the MacGregors in check.

The MacGregors hated this fort and at the first opportunity, in 1745, with twelve Gregarach, Lt Col James Mohr captured and burnt the fort to the ground.  James Mohr also fought with great honour at Prestonpas and also at Culloden with a broken thigh-bone. 

In June of 1746, Albemarle decided to reoccupy it and told Newcastle that it would prevent the MacGregors, from robbing , plundering, and laying waste the country about them.

Major James Wolfe, returning from Hawley's headquarters, rejoined his regiment and was ordered to reactivate the Fort.  He did his work well, setting up sub-posts in the wild hills, arresting lone bandits, and sent soldierly reports every fortnight.  He hated the mountains and the Highlanders, who he thought were "better governed by fear than favour".. 

Note:  In one of the most extraordinary improbabilities ever recorded, it was reported in 1759, after the historic Battle of Quebec, that General James Wolfe, Conqueror of the French Empire in North America, and hater of all things Scottish, died in the arms of a Fraser Highlander, who was no doubt a relative, or perhaps even a veteran, of those same Frasers who had fought so bravely and tragically for Bonnie Prince Charles seventeen years before.

A "Guide to the Battle field of Britain and Ireland" repeats the idea that Culloden was a battle between Scots and English.  This is pure rubbish.  There were more clansmen in arms against Charles than were for him.

If they had known that their land would be subjected to pillage and rapine, they might have lived up to the Gaelic saying "The Clans of the Gael shoulder to shoulder".  Although John MacGregor, the Prince's personal piper, was severely wounded, there is no MacGregor gravestone on Culloden Moor.   The MacGregors who did take part in that epic battle were part of the mixed clans under Lord George Murray's forces.

The "45" was not merely a religious conflict, as many MacGregors by this time had become Protestants.  Regardless, they rose up united under the rightful ruler of Scotland in the face of a world class Imperial Army.

Why did they unanimously revolt against the established government of the land?

Because they had been proscribed into oblivion by the authorities, their lands had been expropriated, they were hunted down like wild beasts, and even their church was denied them.

Under a resurrected Stuart dynasty, they were assured they would be able to become men again and attain the dignity that all people deserve.

That goal would not be attained in Britain until 1784.