I am going to be honest here, but a username does not tell anything about someone. First of all, you don't even have any idea who the person is. You cannot judge a person by their username, because that would make you either have false or true opinions about them, meaning also bad or good reflections of them and we are not expected to have a bad start without even knowing the person. It's a 50/50 chance and not the right thing to do, ever. It's always better to be welcoming with everyone and respect who they are and what they have and if you don't like who the person is in the end, even if they have a literate username, you should always show respect.
That's the lines I usually go through, I'm not a tough heart really. I always like to be soft and proud to be sensitive and strong, or else I wouldn't have the personality I have now. <3