As I said, the text of UFC's most recent lawsuit effectively disproves this. The urban myth that watching is perfectly legal will probably never die on the internet, if only because bringing a prosecution against somebody for viewing an illegal stream is near impossible.
It's not a myth. It's the truth. UFC's latest lawsuit does nothing to disprove this as they are not going to be able or permitted to prosecute thousands of stream-watchers for watching a stream. Their lawsuit is only going to affect the people streaming the shows and the site hosting that streaming. Their lawsuit does absolutely nothing to any stream watchers.
Go find me, right now, the law in which it says that watching a stream of copyrighted material is illegal. I'll wait. You're not going to find it.