what, in short, is so bad about being faithful to what you feel?
I suppose one consideration would be a legal one. We're not legal experts, and for some entities, turning them away for being distasteful or what they believe -- based on what we feel -- could be considered discrimination.
And finally, we think having some consistency is pretty important. Sure, we could just do this case-by-case and that, frankly, would be pretty nice. But it's also not really fair to our users, I think, who should know that we work with some kind of framework in making decisions so that they don't have to worry about us getting pissed off and shutting down their account for (what they see as) insufficient reason.
i'm not a legal expert either, but i am pretty sure that legislation related to discrimination is based on specific attributes (race, color, religion, sex or national origin for the us civil rights act). and being a spammer is very unlikely to be a reason for protection under such laws.
consistency is important if you're doing this enough for it to be noticed. if it's one person in the history of your firm, you could have quietly stalled and no-one would have been any the wiser. instead, you decide to support a spammer and profit from hits on your blog. from that viewpoint you don't come across as a great company, to me...