Actually, you don't. That's the beauty of multi-party systems. Rather than one degenerate party, you have many!

In Germany, you have the Greens, which support the legalization of incest, and which are now part of the government. You also have the Social Democrats, a neoliberal, warmongering shadow of what was once the greatest social democratic party in the world, whose mayor issued an official proclamation honoring a BDSM pervert parade. (And the others are just as bad.)