Astarion doesn't have a criminal background; he has an aristocratic and vampire spawn background. 5e reduces rogues to criminals where a handful of them do honest work at higher levels - this does not work for Astarion at all. Either his class or his story must be reworked, because 5e is overly simplifed and reduced its classes to stereotypes.
As someone already pointed out, he does have a criminal background, and the guy literally disaproves when you defend children against adults who would abuse them. I understand you like the character, but don't try to apologize for him or revize what he is, he might be charismatic. Doesn't change the fact he's an ass.