Isn't Star Trek's genre considered 'Space opera'?
It kind of boggles my mind how somebody could think that the exact same kind of stories are soap operas just because they happen over several weeks instead of one week. That's a silly, arbitrary distinction. And can he really not tell the difference between Sopranos and a crappy soap where they just milk unearned sentiment to contrive anticipation?
I think your friend just came up with the 'soap opera' thing as a flip dismissal to avoid having to make a real argument.