Tangs in general will be aggressive to any newcomers in the tank. Other fish will also be aggressive to newcomers. As a tank owner, you will need to figure out how to get the new fish through the initial aggression without getting it too beat up or killed.
Here are some tricks I use.
1. Re-arrange the entire tank. This resets the fish territories and puts the new fish on the same footing as the existing fish. Of course, many people with wonderfully scaped reef tanks won't like this method.
2. Add the fish using an acclimitization box. This allows the existing residents to see and get used to the new resident, so that when you finally let it loose in the tank they won't give it a second glance.
3. Put a large scary object in the tank that the new fish can hide near but existing fish will be afraid of it. I have used fish nets and eggcrate to this effect.
4. Put a mirror on one end of the tank. The existing fish will be so busy fighting his reflection that the new fish escapes notice.
5. When all else fails, remove the existing fish to a sump until the new fish gets acclimated.