The Hitler/Nazi comparison is one of the most common analogies in informal debates and political arenas.
I mean those are basically the blitz chess versions of discussions where it's about your personal aptitude to be charming, witted, fast on your feet and to produce meaningless hot air statements that sound profound but offer no real angle of attack for other people.
That might be a fun exercise, but it's not really any meaningful. A solid argument should also hold under scrutiny and if you give the other person time to think about it. So that shock value and surprise attacks aren't really working. Like it's not a sign of defeat when you say "hold on, I need a second to think that through". It might even be harmful because speed comes with repetition, but ideally you want to learn something new and interesting or at least expand on what you know, not repeat the same thing over and over again.
And even if your idea is activism and winning a dispute no matter what then you'd probably go for broadcasting and propaganda (propagating your idea) rather than having repetitive 1on1 discussions.
That all being said. It's still a little more complicated than that transitive relation of a bad faith argument along the lines of "your actions" = "nazi actions", "nazis"="evil" therefore "you"="evil" and the non sequiturs you may have along the way.
I mean the larger problem is that it's undisputed that the outcome of the Nazi regime was horrific. That it murdered more than 10 million people and cost almost 100 million lives in the world war, BUT what is however much more difficult to pin down is "what was it about", "where did it start" and most importantly "How can we prevent it from ever happening again".
Like it's still hard to pin down what fascism even is and quite some definitions only list adjectives of the classical fascist regimes (Fascist Italy, Nazi Germany, Imperial Japan, etc). Like seriously it's a mess:
https://en.wikipedia.org/wiki/Definitions_of_fascism
So I'd argue (take that with a grain of salt and if there are more knowledgable people feel free to correct me), that it's less of a coherent ideology and more about something performative. Like a "society at war". Picture something like Orwell's 1984 where the hatred towards "the enemy" keeps the system together, the propaganda, the hatred, the solidarity in order to achieve a common goal, the purpose that glosses over the desperate conditions, but also the paranoia, the ultra nationalism, seeing the enemy in everyone that is not in line, that is not doing their best, that is not necessary for the war but consumes resources needed for the war and the hatred that comes with that due to the sacrifices already made for the cause.
And so "the enemy" is crucial for the continued existence of the war and so for the continued existence of the system that can only justify itself through "necessity of war". But "the enemy" isn't necessarily even a physical being, because if that system would defeat it's enemy then it would be exposed that all the societal problems are still there, none of them are solved and that nothing of had anything to do with any enemy. So at that point the system would either collapse or the ruling class that profited of this unquestioned position of power due to a savior status would just conceive a new enemy and turn the destruction inwards.
However if you'd define fascism like that, then fascism can crop up anywhere and almost everyone could be susceptible to fascism. Wherever you can define an "enemy" and form a community to fight it you could fall into the pitfall of fascism. Either deliberately, in that you stir fear and hate so that people accept your savior status or involuntary as hatred and fear put you in a dangerous autopilot.
And that's a daunting thought and it's not anywhere reasonably preventable as forming communities is necessary and in and of itself not really a problem, people usually agree that solidarity and working towards a common goal is a good thing.
So fascism would start somewhere around making "an enemy" front and center and dehumanize "it". So problem is that can happen rather fast and once such a group dynamic takes a life of it's own it becomes increasingly harder to stop it from the inside. As you'd be in cahoots with "the enemy" and thus you'd receive a lot of hatred too.
So afaik consensus seems to be that if you want to disrupt it you'd need to do it early on:
https://en.wikipedia.org/wiki/Ten_stages_of_genocide
And it's not enough to "fight it" either, as that would just create a mirror image. You'd need to provide a positive alternative.
So comparisons to the Nazis are not just bad faith accusations. Like several definitions of fascism more or less rely on that and pointing out that a group or person has fascist tendencies is not necessarily a judgement of their character and a bad faith ad hominem attack it could also be a necessary warning to calm things down.
Likewise the attempt to argue "it's lost all meaning", "If I'm a fascist and everyone's a fascist, then nobody is a fascist and fascism is ok, cause I am ok" are the much more dangerous bad faith arguments. Because they push back the point at which action is taken and thereby make it much more difficult to take action.
Last but not least, coming back to your question. Well no it doesn't make an argument weaker if it's repeated, if it fits, it fits, if it doesn't, it doesn't. Though if you repeat the same argument over an over again it's likely that people will develop bad faith rhetoric against it. "Oh again the Nazi argument", "nothing but ad hominem attacks", "it lost all meaning" and if they find an audience gullible enough to buy that shit, then this can be a problem. Though that is not really the arguments fault and rather the problem with the audience being gullible or deliberately misinformed and uneducated to not realize the bad faith counter for what it is. You can to a degree rephrase the argument with your own words without distorting the power of it, but if you're unlucky that just leads to a "gotcha! that's the same argument". Well yeah a good argument doesn't have to reinvent itself, only a falsehood should need to.