I'm heavily involved in the FLOSS non-profit world. I have a Master's Degree in Computer Science that has not done all that much for me. I regret getting it.
If you don't plan to teach high school or college, then you would be better served getting a degree in another field. For example, getting an MBA or a law degree might make it possible for you to broaden the range of things you can do. (I'm against getting a law degree, but for other reasons.)
If you want to go into not-for-profit or governmental policy work in computing, getting an MPA (Master's in Public Administration) would be good.
In short, your professors want you to do what they did. Given that B.S. degrees are not as valuable as they once were, it's worthwhile to have some sort of graduate degree, but getting it in another field will expand your horizons and opportunities and also give you more perspective as a computer scientist/engineer.