No.
Broadcasting the fact to the world serves no purpose.
Most people won't notice or care.
Some would find it interesting, humorous, or encouraging.
Some would find it objectionable, combative, or provocative.
A few may strike up a conversation or do something positive.
A few may damage my vehicle as a result, break in hoping to find weapons, shun me on principle, press charges, or otherwise make things miserable.
I prefer anonymity, controlling who knows what about me as best I can.
The net odds & payoff for putting pro-gun stickers on my car are not good.