The partner made you frustrated because they denied your feelings. Your feelings of jealousy and anger are real. They should not have said they did not understand them. They should have said that from their point of view, they could related to a feeling of discomfort, but not to feelings of jealousy and anger. Had they phrased it that way, you would not have been felt that you are wrong feeling the feelings that you do feel.

While you do not have a right to limit your partner's contacts with their ex's, you should have a right to talk about your feelings without having those feelings censored or made appear "wrong".

It is a fine line.

As long as you just want to kill their ex's but do not have a homicidal plan, you are OK.