Very good points brought up by all!
To be honest, I can't quite remember what specifically I was upset and ranting about, which is embarassing, especially since I made some weird conclusions.
I think, at the heart of it, I don't want to have to consider (one-sided) romantic tension all the time I'm watching the show. And I'm really curious if the writers intended for it to be so pervasive. Or even if it is that pervasive - I know I've been influenced by the sheer number of times in interviews Fred has focused on Marshall's being in love with Mary. And even the interviews likely reflect the interviewers interests, or the perceived interests of the audience, rather than his inability to talk about anything else.
Other than that I was being a dork. In the context of their partnership, differing viewpoints on the part of the actors and characters(?) will make things more interesting. I just have a pathological need to have meta-knowledge of any storyline I'm engaging with.