Why would they need to? The events you're describing exist only in the imagination of Mel Gibson and the movie The Patriot.

Nothing of the sort ever happened with Tarleton. He was an effective cavalry officer who led Loyalist troops in a contentious area. He was quite successful and "Tarleton's Dragoons" gained a bit of a reputation as being nearly unbeatable.

That started to change when a detachment of his dragoons was defeated at the Battle of Huck's Defeat (aka the Battle of Williamson's Plantation), and then of course came his defeat at Cowpens.

The closest that Tarleton ever came to committing atrocities was during the Battle of the Waxhaws, and there's still debate over how much was directly his responsibility.

During that battle (which was one of Loyalist militia led by Tarleton vs a combined force of Patriot militia & Continental Army), a time came when some of the American forces tried to surrender. Tarleton came forward to accept the surrender, and was either fired upon by surrendering forces or fired upon by forces who hadn't realized that there were others trying to surrender.

Seeing Tarleton shot at by supposedly surrendering men infuriated Tarleton's men and they didn't accept quarter for awhile until Tarleton could bring them back under control.

The other issue with that battle is that British army doctrine relied heavily on the use of the bayonet, which meant getting up close and personal. To those not used to bayonet warfare, this can take on the appearance of someone who was stabbed while helpless or while surrendering. Many of the Americans were so badly wounded they couldn't be moved and several of those would die from their wounds.

From this single battle Tarleton got the nickname "Bloody Ban" and the Whig forces got the rallying cry "Give them Buford's quarter!" (Buford was the American commander) and "Give them Tarleton's quarter!".

There's never been a hint of any other atrocity that can be attributed to Tarleton. He certainly didn't go around burning down churches with people inside them--that's not something that happened at all in the Revolution. (Yes, churches were sometimes turned into stables or into barracks or fortifications, but they weren't filled up with people and then set on fire.)