The key is figuring out when to use assertiveness vs aggressiveness vs gentleness. And, to learn how to do the first two while being respectful and the third while still insisting on at least basic respect.

It ain't fucking easy. But it is true that assertiveness shifts behavior, as does aggression. People respond to both, and often in ways that seem the same on the surface. But aggression only results in hidden ill feelings, so it's not usually good to use it if you aren't fully sure it's the right stance to take.

Learning that judgement is not a fun experience.