The legal system is built on intent and purpose, so from a legal sense, such distinction is not trivial but its quite normal. What we as a society might want to avoid is ISP that calls a company and say "Would it not be terrible if you lost access to a third of the population in this country. Pay us now, or we will redirect those users to a competitor."

That's already covered by antitrust law

If your traffic shaping rules are different depending on protocol or port number or source or destination IP or AS, then that's discriminatory. Within the space of packet scheduling policies that treat all protocols equally, it is still possible to be somewhat discriminatory and it is still possible to do good QoS. Further and more careful regulations may be necessary, but it is certainly possible to cleanly prohibit a large category of bad behavior without having harmful side effects.