The parts about Sam and his supporting cast getting hate isn't exaggerated. The book does use exaggerated extremist for villians though, but it also has characters like US Agent. Not everyone will want to read about that sort of thing though.I've been trying to formulate my thoughts on Captain America: Sam Wilson and I think that generally I don't like it very much. There's nothing wrong with politically-charged stuff but I feel like it's basically just saying "everything is shit" and it isn't very enjoyable to read.
Part of the problem is that, given the state of modern politics in the U.S., it's kind of weird that apparently nobody really supports him? Like here we are in 2017 with protests happening every weekend and yet in SamCap world most of the people he encounters hate his guts. The book focuses too much on exaggerating the bad parts of the modern U.S. without the proper balance to make it enjoyable. Even in the latter parts of Claremont's X-Men where anti-mutant racism was at its most extreme it was never this cynical.