Genma and Soun aren't really villains. Annoying, yes but villaINS no. There is
also a big difference in being manipulative to get people together and being
manipulative to keep them apart. Especially, when the couple loves each other
and can't admit their feelings. Also, Nabiki dishonors her family just so
Ranma does not become her 
brother-in-law. That is a very low, and evil thing to do.