I see lefty bumper sticks all the time and could care less.
Get a life DUmmie.
When I see one while driving, the following process usually occurs:
1. I see the bumper sticker.
2. I feel a bit annoyed. How long this lasts usually depends on the nature of the sticker (i.e. A simple "Biden/ Harris" will just be for a second or two, whereas a nastier or more insulting one will make the feeling last longer).
3. I remind myself, 'Oh, well, it's a free country,' and progress on my way.
4. I forget all about it a few minutes later.