OP can you articulate how you think restrictions on, I guess, public gatherings of Wahhabists, might be connected to preventing terrorist attacks of the type you're referring to. Like, the perp in question might well be a Wahhabist (I don't know, you tell me), but it's not like at Wahhab-fest 2017 he decided "today is my day to martyr myself". It's not even evident he was radicalized by a local mosque versus the more common story of self-radicalizing online. So it's not really clear to me how your proposal is connected to the problem you're trying to solve, or the analogy you're trying to draw to the United States, where the proposal "don't allow nazi rallies"--not a consensus, by the way--seems obviously connected to "there won't be nazi rallies where things escalate out of control". It's not, incidentally, connected to the adjacent problem of individual lone-wolf nazis planning anti-public or anti-government attacks.
It seems in your haste to make this a round-table debate or whatever you didn't really lay out your argument to begin with, which will probably make some people read the thread as insincere or out of left field.
This seems like an unrelated proposal of whether non-public gatherings ought be allowed to foment anti-government sedition, which is a pretty different question and one probably more closely connected to surveillance powers in terms of enforceability.
This seems straightforwardly illegal under current French law and not connected to something that needs to be changed.
I don't think this analogy is helping you at all and it's really unclear you why you're insisting on continuing to draw it rather than clearly articulating the actual thing you want to talk about. Analogies are devices used to ease understanding of the case of interest by drawing parallels to a case that's already well understood. It's very clear that here you aren't helping people understand the problem you're talking about, you're confusing them because of the tenuous strength of the analogy and the fact that it is being analogized to a case that is currently subject to active debate, not at all something people have a clear answer for that they can port to your context.
Some people might think you actually aren't trying to discuss your case, but instead trying to use the analogy as a cudgel to browbeat people you disagree with into believing their own position on an unrelated issue mandates they make a concession on the issue you're talking about.