I think if you ban the rep than you will not have any reps that will work with any sponsors. So then people can not reach out to anyone but the sponsors for advice or help when a order goes bad. I personally have PM many reps on here when I was looking to start a cycle for advice and met a bunch of great people because of it. I have even had some reps tell me other sponsors to get gear if the sponsor didn't have it or if the sponsor was fixing to go south. One rep saved me money since he new his sponsor was having trouble filling orders.
As far as using the gear exclusively for the sponsor that you rep for is a bad idea how do you know it compares to others out there but don't bad mouth the other gear just because you rep for the other sponsor.