Declining an applicant for being a jerk?

[Larry Gatti]

Is it wrong or not allowed to decline a potential tenant if I think they are a jerk, even if totally qualified? Kind of funny, but I figured if they are a jerk on the front end, I don't want them in my house. And being a jerk is not a protected class. Also while on the subject, is it illegal to require your tenants to be able to speak English clearly enough for me to communicate directly with them (and not a random family member not living there) in order for approval of tenancy? I have no reason or interest in discriminating, but I do have reason to be cautious if I cannot communicate with my tenants. Love to get your thoughts.