You can try to tackle this from a financial, support, or business perspective, but that's not the direction I'd go...
Red Hat funds a large chunk of the GNU/Linux development which you are benefiting from. They make a good product for a reasonable price (enterprise wise), and their competition is good for the software ecosystem. I want to see more companies follow their business model and promote Free Software. Given all that, personally, I think there is some, however small, level of moral obligation to support them if you have the resources. It's just the right thing to do - I think you feel it, and I know I feel it.
Tell your boss that you want to work for a moral company, and that includes things like not exploiting employees, recycling and green initiatives, and things like buying at least one copy of Red Hat Enterprise Linux if that's what you are using on your servers.
When he calls you a "linux hippy", just be like "yeah I'm a hippy, just like all the other hippies that got together, did what most people scoffed at, and created this software from scratch, for free, which you now want to run your whole enterprise on".