I think it's reasonable, but that doesn't mean it's wise. In software (vs food), the things you choose can impact your bottom line, and if you let your dislike of the authors get in the way of your decisions you could end up hurting yourself. That's not to say you shouldn't weigh the ethical implications of your choices, just that "the creator is a dick" is pretty trivial as far as ethical implications go.

But that's not really relevant here. It's a blogging platform among a sea of blogging platforms.

What's a good example of software made by dicks, such that not using it will kill your business? I'm just interested in one example to think about this.

All of the major operating systems depending on your definition of dick is the only one that comes to mind.