It's the easiest way to discredit literally any idea or any person. Just mention Nazi Germany or Hitler or SS or anything like that, and you don't need any arguments or anything else afterwards.

Note that the person doesn't even have to agree with the politics of National-Socialist Germany or anything close it.

Cause now the one attacked has the burden of proof, otherwise s/he'll forever be known as Nazi.

In a nutshell, that's it.