Okay, he better explain his beef, because he's mostly just acting like an asshole at the moment. His argument starts and ends at "summoned creatures are different from humans", which isn't that different from being nervous around animals.
Calling summoners not humans is just prejudice and being a dick.
"Hurting without dirtying your hands" is a bad argument because there's a ton of ways to do that without a magical contract with a mystical creature. Calling it dangerous is kinda fair, except knights and mages all qualify too.
It doesn't seem to be a family thing since his cute cousin seemed to really like summoning. Hmm...