[Solved] Is going into Investment Banking "selling out"?

Selling out simply just means picking a career for money and not love of the role and/or providing value to society.

Investment Banking kind of is "selling out" in that sense since the types of people you are advising and helping tend to big bigger companies. But I wouldn't stress much over what people say. If you enjoy the work, and are interested in IB who cares what people think. 

Not to mention, I believe you can do more good in the world with more money in your pocket. So making some money, while doing something that interests you for a little while, and then giving back in other ways isn't too shabby.