Steve Ballmer nailed it when he said GPL is a cancer. No professional programmer wants to open source anything, but once one competitor does it, he must follow suit to stay competitive.
Firstly your appeal to authority , and then using Steve Ballmer as your authority is perhaps not the best way to start.
Secondly you say that "no professional programmer" - but the statement is false. For starters it's a sweeping generalization which is trivial to show is untrue for at least 1 programmer.
Thirdly the existence of Open Source alternatuve does not make a product uncompetitive. You need look no further than Windows to see that's true. Indeed if we has to list all the commercial software that exists with an Ooen Source clone, we'd be here all day. I'd also argue that Joe public doesn't even know what open source is, much less factors it into a buying decision.
If you are building tools for programmers (already a tiny niche target market) then you need a hook other than Open Source anyway, cause programmers are a terrible target market.
I say this as someone who builds tools for programmers, and who sells commercial into a space that contains Open Source alternatives. And I do ok.