There have been historic instances of corps going against the spirit if not the rule of net neutrality if we have ever really had such a thing in the US

The most open move I recall was made by cell carriers that also owned media companies -AT&T? They would use their cell service to punish or hinder usage of non-owned media. They'd limit the resolution of or throttle the speed of competitors services to their customers. Ex. watch our content at 1080p, but competitors are limited to 480p. That or they would "zero-rate" (not count usage against your data limit) their own services. Ex. watching our content doesn't count against you 1GB limit, but watching our competition's does.

I don't know if it still happens though. I'd be surprised if it wasn't just more subtle now.