I have autism myself. I'm one of the ones who occasionally goes silent during an argument or emotive discussion about my relationships. It's not a deliberate or intentional ploy to abuse, it's not me simply being an arse for the sake of it, or sulking, nor is it due to any other nefarious or underhanded reason.
There are times where I've been in the middle of a back-and-forth with a partner and I've been asked "WELL????" or such. It's elicited absolutely no response from me. That usually resulted in a 'Have you got nothing to say????" prompt, to which I could only answer "what am I expected to say?"
None of this is a deliberately attempt to infuriate or an infantile ploy to close down and avoid a discussion. The simple fact of the matter is that I don't process emotive feelings in a way that enables me to provide and immediate response. Not just an articulate and appropriate response, but any response at all. You can't expect me to immediately reply to something that I haven't thought through and considered, because I do not have a response to give you until that process has been followed through. There's literally nothing inside my head to actually 'say' in response.
I need to go away, contemplate things, quite possibly hours after the event and once my mind is completely cleared of the matter at hand, and only then do I feel capable of evaluating things with any sort of objectivity and providing and articulating a response. There's absolutely no point in DEMANDING a response before then (a particularly unattractive trait in one former partner) because there's absolutely nothing for me to say, so all that achieves is to wind up and infuriate the person expecting the response even more.
It's not that I'm conflict avoidant. I'll happily give as good as I get and then some on most occasions. I'm fairly swift of thought and can usually express myself perfectly adequately on the hoof, but that tends to be when the argument or debate is about matters of empirical fact, not emotions. Emotions are personal, subjective, not the sort of thing I keep an ongoing tally of just to regurgitate on demand. If you ask me how I feel about something and I've not given it previous thought, I'll simply tell you "I don't know" then go away and give it some thought. I don't see how honesty can possibly be described as abusive or 'silent treatment' simply because it fails to pacify someone making unrealistic demands.
I don't believe it's a problem either. I'm not in any way a spiritual, sentimental, or particularly emotional person. Far from being 'out of touch' with my emotions, it's more accurate to say that I'm just not particularly emotional period. I can understand why someone who is the opposite might find that odd, but I'm in no way dysfunctional or debilitated by the fact I'm entirely pragmatic, not prone to becoming emotionally invested in other people's lives, events, etc, and I can usually get right to the crux of a matter and get working on a practical solution immediately because I don't get bogged down in semantics or get easily distracted. In fact, one of the things I find a bit frustrating about a lot of NT people is that they come across to me as ridiculously flighty, unpredictable, and prone to irrationality precisely because of an excess of emotion!
Sometimes when someone says they have nothing to say, or answers 'no' to that question, it's the honest truth, and it's not because they're being an arsehole or can't express themselves.