Sexuality isn't a factor. Jedi aren't sworn to celibacy. The forbidding of attachments isn't meant to control Jedi, it's meant to free them so that they can serve the greater community, without fear or favour. To be a Jedi is to be dedicated in service to others. You can't do that if you have a family since one or the other will always come first and then neither are being served as they should.
Again, all of this is a choice. The Order doesn't trap it's members. Anyone is free to leave at any time, for any reason.
There's probably also a more pragmatic side to it too; we know that force sensitivity is an inheritable trait. So then what would happen if Jedi were to be allowed families, and children? They'd produce more Jedi, possibly stronger in the force, especially if the Jedi inevitably start pairing off with each other. Down that path leads to aristocratic forms, and suddenly a benevolent order of guardians can evolve into an elitist cabal power brokers. Indeed, this may have once been the case, and had been part of the catalyst for the Sith schism.
