Whilst this is probably a joke, it's still a sweeping generalisation of the homeless that paints those in an incredibly unfortunate position as nothing more than cider swigging alcoholics. There are few things that irk me more than vilification of the homeless

I don't want to vilify my fellow Londoners, but to me, that's more a sweeping generalization of London. Getting wasted seems to be the #1 hobby of most the people I know here, no reason the homeless cannot have their share of fun.

It is no doubt a joke, and in my eyes a funny one at that. I wouldn't get too offended by it :) I know the local homeless around this area and there are very few that fit that stereotype