Flying Crane
Sr. Grandmaster
Sure, good points here.I actually agree with all of this. I stopped Wing Chun because it was messing with both my fencing and my kempo. However, I would guess that most arts are compatible to TKD in some way, and while adding a second art could mess it up (aka kempo with wing chun), in general just two arts should not harm the first all that much. And if it is, I would assume that by the time you get 2nd degree black belt in your art you would be capable of realizing that happens and stop it. If not, you are simply getting more experience.
Given that the OP is a young fellow, I think 18? I'm gonna say maybe he is somewhat inexperienced and could use some pointers. It certainly took me a long time to figure this out, and part of the problem was that I lacked the quality of instruction necessary for me to understand these things. In my opinion, there is more poor instruction going on than good, so it's likely a whole lot of people haven't clued into some of these things.
On the other hand, it can be a very valuable exercise to train in many systems in order to figure out what is the best single system for you.
So it depends on what he is hoping to get from it.