When I used to lurk around Tumblr with the NoxLance blog, I noticed many fangirls always had this approach of Leatherface being some kind of poor, sad baby raised in the wrong family and that he did nothing wrong.

In the case of Bubba I can understand that interpretation but I don't really think it's the same for Thomas.
Thomas, from what I saw in both movies and Wildstorm Comics, he's an antisocial. He tried to understand human connections but got rejected and I feel than rather get sad or feeling lost, he ended up thinking the ones in the wrong were them, the others, the outsiders.
He grew resentful of the other townsfolk because they judged his looks. His mother comforted him while his brother/uncle told him to man up and harden.
In the end, Thomas sees his family as his only world and the only one worth caring for, everyone else is meat for his chainsaw.
He does follow orders but he isn't naive or innocent, he does it because of loyalty for the family. He's a butcher that proudly brings food to the table and protects those close to him.
He doesn't regret killing and is aware of his actions.

Fangirls pity him a lot as if Thomas didn't know from right from good, like he's mentally a child. Again, that can be true for Bubba but Thomas is different.
Those fangirls soften him up by adding Hello Kitty stickers all over his face and calling him "baby boy". It's just the typical case of "I can fix him."

It's such a shame to see an interesting killer in such a superficial manner.