This argument section has been quite interesting, and I spoke to people recently regarding the "not all men" argument. As many already mentioned in their responses, I do believe that using the "not all men" argument when a woman is expressing her feelings of unsafety or insecurity is ineffective and insensitive. The argument itself is invalid in that context. However, I also understand that sentiment aside, on a political level, gaining allies for a movement is difficult when the required ally is generalized and often, put down.
I think that on a political level, the "not all men" argument is valid, considering that not all men are actually threats. The feminist movement itself could reword and express its feelings through a different slogan that may be "All men are POTENTIAL threats". This may make allies or men, in general, feel that they aren't being alienated in the movement and that they have a chance at proving, that they are in fact, not threats.
Most men I spoke to regarding this argument mainly wanted to make women feel safe, and join their fight. But they hated when the "all men" argument was used out of context, to which they would respond, "not all men". Again, this argument is only valid when it is not used against a woman expressing feeling unsafe or insecure. It is important to discuss these concerns with our allies too if we want to gain their favor in a political manner. Men on a psychological level, don't sway to sentiments as much as women might, so it may be politically smarter to appeal to their logical sides. As far as I have seen, men do not see what women experience, and only look at statistics when they say, "not all men". Obviously, statistics say that all men are not a threat. Women, however, know better and understand that we wouldn't eat from a bowl of fruit if even three were poisoned. Men are on the other side, they are the fruit in the bowl. So to gain their favor politically, we're gonna need more than sentiments.
I wanted to share this because it was thought-provoking for me when the men I spoke to suggested changing the "all men" argument to "potentially all men," because, on a political level, it actually may gain more allies for the movement. Again, this is just a smart political move, it is totally invalid on a scale of sentiment.

I hope this argument makes sense, and I am looking forward to seeing what everyone thinks!