I have shared my position with many people, both supporters and haters.
Almost all of them react as you did, saying that the Constitution forbids Presidents running for a third term.
If you do not like Trump, you probably already think he's violating other parts of the Constitution , so what makes you think this part would be sacred?
If you do like Trump, my guess is you will probably like him even more four years from now, in which case this term limit thing might actually be troubling you. Plenty of Obama-supporters were wistfully saying, "why does he need to step down, anyway" not so long ago. He may do something like announce that he will happily be running as Pence's VP, and "everyone knows" what that will actually mean.