The gentle art of disagreement has a more robust kin. This seems to be a skill that is being lost. Being nice is not always an option, and some people simply spoil communities and are not to be tolerated.
So what do you do when someone crosses the line from merely rude to being someone who you are unwilling to have in your community?
First think carefully. It is easy to want someone wiped off the face of the earth when they hurt your feelings or pride. That is totally normal, but it is a reason to avoid the person for a while, not a reason that they are a threat to your community. Social combat is something that I am only comfortable using on people who are actual threats to my community.
Second sit down and make a case. This is something that is best done alone. Consider writing down why you think this person is a threat to your community. Write down everything. Go though and look at your list and pretend it is about someone you care about and from someone who you don't know well. Evaluate each item from that perspective. Chances are your list will get smaller, more objective and less about you and yours. That is a good thing. Often the most powerful things you can say are the sort of things a person is likely to have noticed themselves.
Oh and it shouldn't need to be said but be sure you are as scrupulously truthful as you can possibly be. You might need to eliminate items you cannot properly attribute. This is your reputation you are putting on the line be sure that each statement in your case is something you are willing to stake you name on.
Now you are properly armed. It is time to do combat.
Go to an even you would normally go to where your shared social circle is present. Wait until the person in question comes up. Say you don't choose to associate with that person. Next make your case against them in one or two short powerful sentences. Do it quickly and clearly and be sure that they know you will say that to anyone. Including the person you find offensive.
Repeat as necessary.
Some concrete examples of social combat-
"I don't choose to associate with him. I understand how someone might have to kill in that line of work, but he brings it up unprompted and with pride in his voice. It makes me uncomfortable that he seems to think he should be respected for that."
"I don't like associate with her. I have never heard her speak of anyone she actually knows with admiration or approval. I have heard her tear in to friends new creative endeavors when they are at their most vulnerable. I don't want to subject myself to her constant critique nor is it what I would wish for my friends."