Remember, when setting and enforcing boundaries, the calmer and quieter you are, the more effective it is. This is true no matter what neurological situation you're in.
Setting boundaries for yourself and communicating them with other people are skills that you must practice to be effective at. Often when you get started, you might come off aggressively or with language or tone that is off-putting or offensive. Reflect on it and make adjustments as you grow. Also, some people are just jerks.