Okay this completely leaves out context and is just general bullshit:
First of all Tony didn't build Sentinels, Red Skull did using info he stole from Iron Man. Second of all, the Avengers as a whole weren't mad at Magneto just Rogue and Scarlet Witch. More importantly they were mad because Magneto is trying to change and be a hero. Him extrajudicially executing Red Skull (he had no way to claim self defense and was pretty clearly motivated out of personal anger rather than any sort of "he'll just get away" logic) was seen by them as a sign that Magneto was just lying and hadn't actually been trying to change. Further his recklessness in killing Skull released Onslaught (long story). It was an important character moment for Magneto that ended with him realizing that he wasn't doing enough to be a true hero and setting him down a better path. To claim that this is what happened or that Rick Remender is a bigot for writing Magneto with human flaws is disgusting and a complete bastardization of what happened.

I don't remember tony having anything to do with the Sentinel program. And Magneto has his head so far up the mutant-supremacists mindset that he might as well throw out the term "master race" every 5 seconds.

Killing the red skull is a stupid reason to hate the man though.