Yes, those New York City subway ads are racist and despicable. But hey, that is free speech for ya. Not everybody feels the same way, yet we all have equal rights to express ourselves. 'They' get to say what they want, and 'we' get to say what we want. Deal with it. And then fight your battles appropriately. With words. Arguments. Debate. Collect some money for a counter ad campaign. Out-smart them verbally. Not with vandalism.
I thought all of us 'decent' people had decided that was the adult way to deal with situations like this, when those 'savage' muslims started attacking American embassies* last week, because someone insulted their prophet. They were 'barbaric' in that they were incapable of formulating a proper response in words (or perhaps an equally offensive video - poorly made, of course) and chose to fight with their hands instead of their brains.