Conclusion: be polite, don't be a dick.
Questioning people's cherished fantasies and telling them they're wrong is going to be perceived as "dickish" no matter what tone you use. Believers interpret
any expression of atheism as "uncivil."
The theist definition of a "militant atheist" is "one whose lips are moving." Worrying about "tone" and "being a dick" is concern trolling, and Phil Plait fell for it. The goal is to poison the well again skeptical and atheist discourse by referring to any honest expression of it as "being a dick."