Because theists vote (or run the government directly) or at least men use religion as an excuse for power and suppression. If someone tries to get a gay bar shut down because its a den of sin then religion becomes the issue, not homosexuality.Also while you are right that the debate between the two groups are not on the plane, atheists do display a willingness to talk about religious issues that is as intense as a religious person. If this is all nonsense, then why is it so important for atheists ?
I, as a near life long atheist, do not enjoy such debates with a true believer, because their minds are completely closed. What I do enjoy are such debates with believers who do not simply dogmatically believe on faith alone.