Right but to go back to the beginning, we shouldn’t target short people per se, but the behavior of shoplifters, if the shoplifters in fact end up being predominantly short people while not looking specifically at short people I think it’s not immoral.
But the learned behaviour will be short => likely a shoplifter. Short people who don't shoplift will have to deal with being suspected of shoplifting at a higher rate than the rest of society. You could say that's just a fact of life, a minor thing, but it's still a privilege to not be in that group. If you then belong to multiple of these groups (dark skin, poor neighborhood), you become a primary target without ever having any intention of doing anything illegal. It's not immoral per se, but it does not set the stage for a fair society.
It does add some unfairness I can see that, but I’m not sure it’d be permanent. Is it possible since short people are caught at a high rate this would deter the thieves who are also short and then through feedback the system would begin to target thieves who are also tall?