If both parties are consenting adults, they can do whatever they want, no matter what their body looks like. What people look like is the least problematic thing that could come up in a relationship, sexual or no. Things like lack of consent, objectification, emotional/physical abuse and so forth are much more problematic than having sex with a consenting partner whose body is different from yours.
Of course, consent implies the partner is -able- to consent, so I wouldn't consider sex with a non-humanoid race problematic. Maybe weird, in the "I don't get how you can be attracted to that" sense, but not problematic. What is problematic is having sex with animals, since they can't consent to it.
That being said, obviously if the size differences are too brutal, you probably can't have certain forms of sex without mauling the smaller partner, so you'd have to get creative. As long as both partners are consenting and happy, power to them.
Of course, consent implies the partner is -able- to consent, so I wouldn't consider sex with a non-humanoid race problematic. Maybe weird, in the "I don't get how you can be attracted to that" sense, but not problematic. What is problematic is having sex with animals, since they can't consent to it.
That being said, obviously if the size differences are too brutal, you probably can't have certain forms of sex without mauling the smaller partner, so you'd have to get creative. As long as both partners are consenting and happy, power to them.
