Picking your nose at the table and scratching your crotch in public are also simple actions. But I guarantee that neither of these are done by anyone who wishes to be considered anything other than rude. It's a matter of context. Do whatever you want ( as long as its legal) in private. But moderate yourself in public or accept the judgement of those around you.
Snapping your fingers at anyone is demeaning, reducing them to the level of an animal that you command to come at your beck and call. And that is offensive.