I'm a white dude, so obviously I can't speak for black people and it's not typically appropriate for me to get super offended about this on your behalf, but personally there's something so jarring to me when people use "blacks" as a plural noun. I think by prior experience, when I hear it put that way it subconsciously primes me to expect the person speaking is angry and racist. I've just heard so many people say it that way in agitated tones.

Then again, I've also definitely heard older people talk that way and they don't seem to mean harm or be angry.