do you give away your services?
Of course not.
Should open source software be illegal?
I don't, but if someone down the street offered to do exactly what I do (or do it almost as well) for free, I'd have to figure out a way to deliver enough value to make it worthwhile for customers to pay me.
If I couldn't do that, I'd have to find another line of work.
Those same choices are open to the proprietary software industry.