If you don't have a problem with "fuck nazis", then we're good. If you see "fuck nazis" and want to defend them, fuck off. If you're good with "fuck nazis" then we're good.
I agree that we have to be careful about who we call nazis, and who they call nazis, but if you get offended by the phrase "fuck nazis", without further context or identifiers, then I'm ok with saying fuck off.
Yeah, I saw the shirt. It's not a swastika or anything, but it is celebrating the Olympics hosted by the fucking nazis, using the official designs from back then (I assume on that part, it's what it looked like to me, as I am not knowledgeable about the decorations at the nazi olympics). So, fuck them.
And yet, you are not explaining your position. They were selling nazi propaganda, and should be called out for it. No "what about" or "this is also bad". We have a nazi problem. Fuck nazis. Fuck nazi apologists.
Honestly, I hope it is more deterrent than anything else