Exactly, depends on how you say it and what is the context. One of the posts on this thread mentions taking 20 minutes longer doing a dungeon because the healer isn't doing any dps... That is when it's an offence, is the healer performing his duties and keeping everyone alive? You so, you can politely ask him to trow a broil or whatever.
Depending on how the interaction goes he doesn't have too, the healer will have 10000 excuses at his disposal not to do so, and if you file a report ( which square encourages you to do so) I doubt anything will come out of it, if nothing else he can just say it's too hard for him to keep switching between the party to keep everyone alive and the monsters to keep doing damage, at the end of the day, he did his job which was to heal, the group survived and finished the content, although according to the previous post 20 minutes later.
On the other hand if you ask a second time for the healer to dps he can file a report against you, and its most likely being considered harassment, because you have already states you opinion, request, advice and you are now keeping pressure on the innocent healer that was just trying to help the group.
I for one won't be telling an healer to dps... Whatever you do it's up to you.
But back on topic, square enix does not want that they have said so on multiple interviews, every player is awesome and it's doing a great job. They have just updated the TOS precisely to show this.
Even if you are part of an FC or static and you push the border and someone reports you, you will receive a penalty. Do you really think they will implement a way to measure people ...