This is a thought that I had a long time ago that makes a lot of sense to me. This is about the relationship between beliefs and personal identity.
If you are in a conversation with a feminist (but this happens regardless of the ideology) and those beliefs are part of their personality, if you criticize or suggest something wrong with it, you are questioning the identity of the person you are talking to. Any person who turns an idea into something that makes part of the person's identity, creates this scenario. You can raise valid points by demonstrating fallacies or negative points in a particular ideology. That is fair. The problem happens when you are talking to someone whose its identity relies on those beliefs being true. By questioning specific ideas, you are questioning the identity of people holding those ideas as part of their identity. That is why debating feminists turns very fast into aggressiveness.
This is just a thought, feel free to make me wrong.