Feminism has nothing to do with the sheer existence of women. Feminism is about equality between women and men. Nobody who disagrees with feminism also believe all women shouldn't exist, and not believing in feminism does not mean that you want to be in a world without women.

Also, that's incredibly offensive. Your justification for being feminist shouldn't be "I'm feminist because I want to get laid," or "radical feminism is hot," because both are inherently not in line with feminism. Feminism is about seeing women as people, not a possible partner. If your reason for being a feminist is to sleep with women, that inherently breaks with the concept of feminism.