I never claimed this. My argument hinges on the fact that he has the right, in certain circumstances, to make violent threats as opposed to normal citizens.
The TOS is written for normal citizens because it is indeed illegal for normal citizens to do so. And I therefore agree with you that the TOS technically does not allow any violent threats on twitter.
I do not think it is unreasonable to allow the President to communicate his threats on Twitter, a modern means of communication. I think it's actually a good thing to allow, for this and all future presidents.
Again, letter of the TOS vs. spirit of the TOS.