My general impression, possibly out of ignorance, has been that there have always been lots of these and people (read: me) were just unaware of them. Some, like this (and "88" on usernames) are sometimes (often?) legitimate but have also been used as dog whistles... and fascism stains everything it touches.

Indeed, it's the fascists and bigots who appropriate words and employ ever shifting rhetoric to avoid being labeled as fascists or bigots and to try and conflate their ideology with as many pre-existing ideas as possible who are to blame for this linguistic treadmill, and not the people who point out that dog whistles are real.

In the same way security researchers are not responsible for security vulnerabilities, but may take heat for pointing them out.

That being said, just because they try to appropriate the terms doesn't mean it has to work. They can be reappropriated back to their original meaning.

The vast majority of it is just to rustle the jimmies of people who use terms like fascist. The more butthurt people get about it the more you'll see it happen. They're not actually fascist dog whistles. It's them signaling to each other that they're not one of you.

That is not true. They use these terms among themselves to denote things. Their opposition is not intended audience at all.

Moreover, when unopposed, nazi and antisemitism do not die out. Instead, they get stronger and larger in numbers. It is an actual ideology and those who believe it are actively trying to spread it.

Anything spreads easily if there is enough propaganda directed towards it.

I heard crypto-jew as insult to pro-jew (read anti-anti-semitic) fairly frequently and did not heard it in any other context.

It is not "reanalyzed" as such. It is that antisemitic use it as such.

Maybe your frustration and ire should be directed at fascists that generate/co-opt these terms to begin with.

Same way you navigate everything else, by paying attention and making frequent and small adjustments as you acquire new information? You chose a good metaphor: selecting a straight line and expecting not to deviate from it is not "navigation" in any useful sense.