What I feel about this episode that I will give a more in depth detail in my blog review, but I honestly liked the episode and especially loved the angle they took Big Mac's character in the episode and the lengths he went to spend some time with his little sister he wanted to make proud like he used to.
I didn't mind the drag outfit as I felt it handled it well enough, and I liked that humor not dead yet despite how politically sensitive many folks are. As for the cries of the episode involving a transgendered Big Mac, I don't think so as a guy crossdressing =/= transgender, especially in context that he's doing it because he wanted to participate in a contest where there was no stallions or colts involved in an event called 'sisterhooves social'. Speaking of which, honestly I'm still wondering what is this cry for gender equality and stuff. Rainbow Dash's comment I felt was actually very gender equality considering it's a reverse on the trope of a guy declaring that just because he's competing against a woman doesn't mean he has to hold back for her. She's putting it out there that she is not going soft on Big mac in a race just because he's a stallion, I don't see any issue with it. Finally, that whole quote of Big Mac not behaving like a 'lady' quote, I'll need to watch it again, but I honestly felt it was more pointing out that he should've behaved with decency and respect as one would expect from an upper class lady rather than wreck the course like he did in his attempt to win it.
Really, I'm kinda disappointed that many people are taking things out of intended context or are taking things more in depth than it really is just so it can appeal to their sensibilities or justify feeling offended or so.