It is quite natural in any competitive Game that things can get heated up really quickly if given the right spark to do so. Sure, it isn't nice to be on the recieving end of being called a Noob, a Wintrader or something far worse, but most of the time, all those People ever do is vent for a couple Messages and then after one Hour, they completely forget you even exist. Even if you dont want to hear any of this stuff, all you need to do is use the Blacklist function and you already got your peace of mind sorted out.

FFXIV always had and still has, a good number of People who will still call you out on the most mundane things, just to passive agressively tell you to get gud and how much of a scrub you are, this happened in EVERY Feast match and it will most certainly be that way in Crystal Conflict as well. Personally, i take big joy out of those messages simply because how silly some people can become, but i can only advice one thing about toxicity in general:

NEVER take it seriously. So what if some random guy talks shit about you on the Internet? what is he going to do? shoot your dog? call the cyberpolice on you to arrest you for underperforming on FFXIV PvP?

This Game makes "inappropiate Language" a way bigger deal than it actually is, what happened to the old saying "Sticks and Stones may break my Bones, but Words can never hurt me?".