DPS display could easily be solved with a system already in game.

[Welsper59]

But why is removing a player from a party for low DPS is somehow unjust if it results in inability to clear a duty?
Coil... yeah, whatever. Cloud of Darkness, Steps of Faith, Ramuh EX phase 2, Amdapor Keep HM, goddamn Titan... These all feature DPS checks that can easily lead to a group-wide failure when not met.
The game does expect you to perform well already, being bad isn't against the ToS but it is against what game actually expects you to do.
Sticking your head into the sand with "you can't stop me from having fun" is exactly what leads to 50-page threads like "Steps of Faith is too hard, QQ". It's just hypocritical.
I know this sounds a bit like "You don't have anything to fear if you don't have anything to hide", but developers chose to put the aforementioned DPS checks in front of the players, even those that don't do what is officially considered the raid.

Depending on what's actually being said, it's not as hypocritical as you might think. Content outside of Coil is hardly what I would call a DPS check. Even with Cloud, properly/decently performing DPS (which does not, by any stretch of the imagination require parsing) will not prevent you from victory. Parsing is there to give you the extra bump in output timing (maybe around ~50 DPS extra in some cases), whereas knowing your class and rotation/priorities will get you the grand majority of output. Why do you believe parsing is the bulk of your output? I didn't take advantage of finding out my output at all in this game until recently, and right off the bat, I was pretty damn close to what I should have been with the gear I had.

My point is that it isn't objectively preventing anything at all. Groups will disband and reform without the low parsing dps, no harassment needed.

The point here being is that it isn't the "third party programs (parsers)" that SE is banning you for in this instance it's because you used it to harass someone. Square knows well that people use parsers and do not care, they just don't want you harassing people with it. But even with all of this there is still not a valid reason to not let a person see their OWN dps numbers. None at all.

"This is something you would NOT be able to do very easily if parsers were officially allowed"

^^ This is nothing more than assumption and there is no objective proof that allowing a person to see their own dps will make it "harder" to stop people from harassing each other. It's a non-sequitur. Harassment has and will be dealt with the same way it has always been.

Oh no no, I agree. It doesn't fully prevent anything at all. People are going to be... well, people. Laws are there to protect and prevent, but it doesn't mean we're not going to break them from time to time. I'm pointing out that the fact it's not officially allowed is merely protection, and as we all know, protection is not guaranteed to prevent. It's merely an extra layer, and given that SE knows about how useful parsing is when used appropriately, it's exactly why they don't mind people using it... just don't misuse it. Again, the current mentality is that its unofficial status keeps it a means to protect from those negative situations and reduce the occurrence of singled out players, nothing more.