Personally, if I engage with these sorts of folks, I tend to challenge their assumptions where they come up vis a vis conversation. I challenge assumptions, ask questions that allow me to delve deeper, and state my perspective with as much candor or guard seems appropriate to the situation.
There are times that is not appropriate, and dealing with racism, patriotism, and xenophobia needs action, a quick perusal of IGD or Anews will give ideas of what this might look like in different situations. I am wary of antifa as a primary focus for anarchists, and I live in a particular place where being actively anti-fascist does feel like something that anarchists need to actively engage in, even if I find no personal drive to engage in street fighting, etc. Living in a place that has been identified as a future aryan homeland creates particular... challenges?... opportunities? IDK. It is hard to dismiss the actions of antifa living where I do, but I am wary.
(i might amend this answer, as I am not totally happy with it and suspect I am not answering your question, but I also might let it sit and let comments allow me space to further hash out what I want to say)