Don is a terrible human being, but it's pretty clear he's NOT a homophobe. He saw Sal post-coital with some dude, and said nothing about it. He intentionally let Sal keep his dignity, safety, and job. Watch the scene where he fires Sal again. Don makes it pretty clear that he would have slept with a female client to keep her business and that he expects it the same from Sal as well. To deduce, solely from "you people," that he's a homophobe, despite all his past behavior, is really poor character reading.
And his tirade against Peggy this week was one of his most reasonable (albeit still not *actually* reasonable). Credit always goes to the person at top. That's how business works. In law, the trial attorney gets the reputation, even though most of the leg work is done by associates. On TV shows, directors/head writers get the credit even though they don't do the bulk of the writing. Peggy is one of the team members; Don is the leader. He gets the credit. But, like Don said, Peggy is young, and she will get her credit later when she rises up the ranks. That's the system, and Peggy doesn't get an exception.
But he should still say thank you.
