Both sides have valid arguments.A cheating girl will cheat whether she hangs out with male friends or not, and a loyal girl won't cheat no matter how many male friends she has. It's dependant on her own personal moral code, and you can't really change that much. That being said, this discussion is really just a matter of possessiveness, and why you feel that it's right, not whether she'll cheat or not.
A cheating girl will cheat and a loyal one will not.. But in some god forbidden moment of fun or being high or drunk with some guy friend who essentially is platonic.. some things could HAPPEN unknowingly in the HEAT of the moment. This is what is DANGEROUS.
Her hanging out with guys .. be secure.. dont be insecure.. But, if she puts herself in situations where she might lose control. That COULD possibly cause something without her really wanting it, but more just by accident.
She needs to learn to RESPECT not YOU.. not RESPECT the RELATIONSHIP and not put herself into situations.
PS: Bottomline when such situations arise.. YOUR DESIRABILITY and PRESENCE in her active life can cause her to GET OUT OF THE HEATED MOMENT and prevent cheating. The lack of the same could make her get into it more.
We humans are fvked up.