My recommendation is to either refrain from using it, or use it with the knowledge that it's just an anti-communist pejorative. I don't recommend trying to claim you aren't an anti-Communist while using the modern version of "pinko," when everyone hears it as such.

My biggest recommendation, though, is to just visit places you feel are "tankie" and try to ask questions in good faith. Make a Hexbear account, and participate in the general megathread, browse the news mega, or just lurk, and then you'll get a better view of what these "tankies" are actually like when they aren't in an environment hostile to them and dedicated to misrepresenting their words at every instance.