That is a generally accepted principle. There are exceptions, of course -- notably when that silence is coerced. However, if I choose not to object to a particular claim, then it may reasonably be assumed that I accept that claim as correct -- or, at the very least, that I have no opinion on the claim. However, Rhomphaia manages to find an invalid invocation of the principle. Specifically, she invokes the principle and blocks response.
"[It's] not honest to set up conditions when someone has already said they're done talking."
Well, strictly speaking, I am stating my beliefs about why he has taken his ball and gone home. If he disagrees with those beliefs, I am not blocking him from saying so.
"You can't just tag on a clause when they've walked away from a conversation!?!?"
Of course I can. He departed in dishonesty and I can certainly tag on a clause to point it out to those who are paying attention.
"...Talk about false dilemma- you gotta stop that, seriously."
The list of logical fallacies is not simply some grab-bag that you can throw items from when you feel like it. I made my assessment for the reasons for his behavior. He can challenge them or not (on your post, of course; he is currently not welcome on my blog) at his discretion.
"No need to respond- remember your rule- silence equals agreement,, hmm?"
That would work a whole lot better if you weren't blocking responses. However, I responded where I could. It looks like I don't agree.