If a player is show-boating, yes. If a player is crowding the plate, yes. But not just because someone is a rookie. I don’t seem to recall Kemp getting plunked by some chicken*** pitcher, just because he was a rookie.
There was always a code to these things. Hamel doesn’t even know that. Why do you think virtually every old-time player has come out and said this wasn’t old school baseball, but was classless and stupid?
Few rookies have come into the league getting accolades Harper is getting. Hamels just wanted him to realize he is still a rookie with a lot to learn.
This happens a lot. But most pitchers don't admit to doing it so it isn't made a big deal of in the media.