Nobody is doing a campaign here promoting it, you are exaggerating it. Who would even benefit about promoting a specific sexual preference?!
It is just a major fact that in our society everybody can basically live the life he wants to, and this fact distinguishes the western part of the EU from a lot of other countries. And yes, we like to point out that everybody here can live a free life.
I might just turn this discussion around, for example in Russia there are actual campaigns against homosexuals, so I might just ask: Why are they promoting heterosexual behaviour? Just because 90 percent of mankind likes strawberries, there should be a law forcing all citizens to daily eat strawberries?