Hello, In response just to the title of the post/question alone. I will tell you no it is NOT illegal to taunt or intimidate the enemy team, In fact it's used in all sports and esports. However, you do have to be careful on what you are going to say. My best examples are:
What not to say to an enemy team:
"Wow you guys suck, you must all be a bunch of FUCKING RETARDED C U N T S!!!
"I can't believe guys are losing SOOOOOOOOOOOOOOOO fucking bad, noobs. "
"GG Fucking Nerds surrender already, you guys are gettting rekt and go cry to your mommy, oh and then kill yourself"
What may be acceptable:
"Get rekt" (Wrecked)
"1 v 1 me bro"
"Woo hoo, we got first blood, rekt"
Though the first group of comments fall under a few different reports. The second group could also be reported, but really only for "unsportsmanlike conduct" But even that is a stretch. I would also say that, the second group of comments are completely acceptable and are not reported as much as the other group of comments.
It could also depend on how emotional people are themselves. Everybody's emotional status is different. Everyone responds differently to intimidation and trash talk. However, you generally never really know what the other persons emotional state may be at that moment. Long story short, just have respect for others and choose your words carefully.
Again, these are just my opinions on the matter and everyone else is also entitled to their own opinions as well. I hope this helps a little bit in clarifying things more.
Sincerely,
Swallower