This kind of thinking is dangerous and scares me more than the dragnets themselves. There should be nothing suspicious about a citizen exercising their ability to choose from providers. As an analogy, I find it on par with thinking that hippies/minorities/whatever are somehow subversive just because they don't fit your idea of normal.
And yet hippies were monitored, and yet it's plausible that protecting your privacy does make you suspicious.
So I understand that this is scary, but I don't really understand why you consider this kind of thinking dangerous. If it's true, or if there's a good chance that it's true, then shouldn't that knowledge be acted upon, or at least considered, however scary?
Or am I misunderstanding you and are you just stating that in general you hate this situation?
On the one hand your argument makes a lot of sense to me, but on the other hand using an email provider that is not one of the popular ones might in itself make you seem more suspicious.
And intercepting your email correspondence, no matter the provider, might be so trivial to the intelligence agencies at this point that they might be doing so already anyways. It's not unlikely that they'd be 'scanning' Fastmail email more intently than gmail, precisely because of the kinds of people that have security concerns.