Rudolph was the victim of bullying & discrimination. The other reindeer called him names & excluded him from their games. He was singled out for harmful treatment.

Then Santa picked Rudolph to lead his team because of his red nose, the same characteristic that probably caused his exclusion

The song says the other reindeer shouted out in glee, "Rudolph, the red nosed reindeer, you'll go down in history".

But that's not how things work in the real world. They probably muttered, "Rudolph is a red noser"

But were they brown nosers who gave an outward show of approval to the boss's decision but seethed with anger