I think you just have to understand that most of the anti-cropping "lobby" (for want of a better word!) come from countries where cropping is illegal, and, I would go so far as to say, considered barbaric. It's a cultural thing, like circumcision (which, incidentally, can only be done in Ireland for medical reasons, you can't elect to have a child circumcised, even for religious reasons).
I would compare it to female circumcision or foot binding - it is acceptable in some cultures whereas in others it is viewed with disapproval or even horror. That is the way most Europeans would look on ear cropping - it's just not acceptable practice here, and that's why we sometimes have a hard time realising that it is still seen as perfectly normal elsewhere.
Dew claw removal is also not practiced here, and I've a feeling that a ban on tail docking is on the cards too (it has already been introduced in the UK recently).