I don't think this is cartoon is particularly funny. When I read items like these I always ask some basic questions such as: Who's the audience of this paper? and Is there some context that I'm missing?

UK Pink News reports:

Following the Snicker incident with a Mr T ad being pulled from UK screens after US queens complained it was hostile to gays, some people in this country have take exception to this cartoon from nationally distributed free paper METRO, published yesterday. You can join the debate here.

Is this cartoon homophobic? To me,  it's not homophobic, however, I can see why some people might take offence. Gay people have very little representation in everyday media like this cartoon strip and when this writer decided to mention gay people he did so with ridicule.