I don't think it came across like you were bashing James Marsters at all, and if someone wants to unfriend you for having an opinion, then you're probably better off not having them as a friend anyway, imo.

I wrote JM a short letter just now, and I've just mailed it. I read it to a friend over the phone and she said it was mature and it didn't sound like I was pointing fingers, which I hope is true, and I think it gets my point across, without sounding accusatory, because I still like him as a person and admire him as an actor.

-Glop