Judging someone/something quickly is in our DNA to assess for risks and ensure our safety/survival. It just so happens that visual stimuli is one of the easiest ways to determine threats. When we see someone approaching that has mechanically altered their appearance, vs. someone who hasn't, our brain processes it subconsciously and consciously. It may manifest consciously with many of the thoughts shared here, based on past experience or media depictions.
Now, when/if there are more people with tattoos than without for a long time period, that is when things will get interesting.
The way it's going one day folks will feel intimidated or threatened by those without tattoos.
"Don't talk to the man without tattoos sweetheart, they can't be trusted and you don't know where he's been"