I guess the message is that, as well as being the focal point of the Rugby World Cup this autumn, Paris is also still the capital city of romance, but perhaps you need to be French to really "get" the message or the humour.
Don't get me wrong - I don't find the picture at all offensive (as I'm sure some people do) and, to a degree, I can appreciate its humour, but as an advertising campaign my considered opinion is that it's pretty crap. Who, for instance, are they attempting to appeal to? The gay community? The rugby crowd? Brits in general? And would an image of kissing rugby players convince you that Paris was the place to visit?
Personally I doubt this works for anyone but the fact that we're talking about the campaign means that it's well on the way to succeeding, whatever its motives or merits.
Having said that, how utterly French is all this?