what's wrong with enforcing illegal immigration laws?

not a trump supporter, but one critique i never really understood is illegal immigration.

it's even in the name, "illegal, immigration". any type of logic would say that if someone is caught immigrating illegally, they would have to be deported. it's been a thing way before trump, every president before him including obama has enforced illegal immigration laws.

can you really blame trump for enforcing these laws? coming to the united states illegally, (key word), is not legal. so what's the issue with deporting those who didn't come to america the legal way? and what do you expect? do you really expect the cops and the feds to not enforce legality? it's just ridiculous that a lot are surprised of the results (deportation) of doing something clearly illegal. thoughts?