Hi carrust, A tattoo won't change the son (man) you've brought up well, Do you think by getting a tattoo it will change him in any way? Maybe you're concerned he might want more, or even move onto piercings.. but even if he does, he's still your son and as long as he respects you and loves you what more could you ask for?
I'm sure there are things you've done that your parents didn't exactly agree with, but at the end of the day, as parents we have to accept the fact that our children are people in their own right, they don't have the same views and ideas as we do. Changes in social acceptance has created a way forward for those wishing to express their individuality - something that was once called 'different' (and about time too I might add)
He's your son, could you really justify throwing him out and potentially not seeing him again or having very much contact with him all because of a tattoo?