I'm demanding that my ex boyfriend not bring his new dates into our common workplace, parking lot, break room, etc
Do you have a reason why you don't want your ex boyfriend to bring his dates about?
Because I don't want dumb and ugly girls to ruin my mood every day
It is not your place to tell your ex boyfriend who he can't bring to your workplace. Since he is your ex, it is not your business who he brings with him wherever he goes.
He's a dick, so I don't care.
I know he is your ex but you should try and be civil. You shouldn't tell your ex what to do though. If you find it hard that he is bringing his dates to the workplace then maybe you can have a word with management.