Okay, here’s the problem with the idea that oppressed groups can “alienate allies” by not being nice enough:
You shouldn’t be an ally because oppressed groups are nice to you. You should be an ally because you believe they deserve basic human rights. Hearing “I hate men” shouldn’t make men stop being feminist. Hearing “fuck white people” shouldn’t make white people stop opposing racism.
Your opposition to oppression should be moral, and immovable. Your belief that all humans should be treated with equal respect shouldn’t be conditional based on whether or not individual people are nice to you.
This is true, however: Don’t let tumblr purity culture tell you it’s ok to attack and harass people who call themselves “allies” if you catch them doing something problematic. Tell them, calmly and without accusations or name calling, why the thing they did was wrong. Somebody who’s in the process of learning how to be a good ally shouldn’t have to suffer through some angry tumblrite’s verbal abuse every time they slip up on something. They’re learning. Act as an educator, not an enforcer.