You are right
The text says the following
Redirect Attack. When a creature the goblin can see targets it with an attack, the goblin chooses another goblin within 5 feet of it. The two goblins swap places, and the chosen goblin becomes the target instead.
The text doesn't mention that "another goblin" has to be an ally of the Goblin Boss, then it would say "another allied goblin" or something similar, and it also doesn't say that the goblin has to be opposed to the creature attacking the Goblin Boss.
Therefore the Goblin Boss can also choose a PC Goblin that happens to be close by or an NPC that is opposed to the Goblin Boss.
As a DM I wouldn't do this because it feels to me like this is not the intention behind the ability. I have always imagined this to be "grab an unsuspecting ally and hold him in front of me as a shield", which is already difficult, but grabbing an enemy or hiding behind them is a lot harder because they are actively fighting you.
Also, as nitsua60 mentioned in the comments, the MM was published roughly 3 years before VGtM, which first allowed PCs to choose Goblins as a race. This means that the fact that players could play Goblins was likely not taken into account - because at that point there was no such option - which means that they didn't have to think about this when wording the ability and none of the playtesters could have come up with this usage inside the framework of the existing official rules.
Additional information from Jeremy Crawford, mentioned by Rubiksmoose:
@JeremyECrawford Could an enemy Goblin Boss use its Redirect Attack reaction to swap places with a goblin PC or PC-allied NPC?
The goblin boss's Redirect Attack doesn't specify whether the affected goblin is a friend or foe. It works on any goblin within 5 ft. #DnD