I just ignore any negative comments I get from people. 9 times out of 10 they are just jealous poor children who would box anyway if they could afford it. Its not worth trying to explain your motives to someone who is incapable of generating $45 a month.
The only arguement I have ever used in response to people is that it is cheaper to have 5 wow accounts than it is to have a good sky tv package. With that said there are a few boxers on my server and I very rarely even get noticed.