If one harms no one and practices ones religion - that is respectable and well worth respecting, whether or not the god or whatever in question really exists. One can respect human culture, tradition, and experience. Religion, belief, spiritual experience, etc, are human experience and can be respected as such whatever one may believe.
I wonder if this is a key: to skip condemning others, to simply practice one's religion, live according to one's beliefs. If, for instance, one's religion rejects homosexuality, or usury, or the eating of pork, refrain from doing the thing, state with simple dignity that one refrains because of one's religious belief.
Major and minor bad nastiness has been done in the name of religion. The inquisition was not nice. Of course, the Stalinists and others have proved that one does not need religion to be a cruel abusive bullying shit. Or, a minor rude jerk.
In my experience, kind loving believers and kind loving non-believers have very much more in common with each other than they have in common with the mean-nasties at either pole.
I wonder about the motivations of people who are abusive in condemning what they perceive as the sins of others. I speculate: Perhaps they have some muddle-headed feeling of diverting the wrath of their god by pointing at other targets? Or perhaps they hope that all the loud-mouthed hypocrisy will hide their own sins? (Perhaps I am underestimating the dynamics of groupthink; I tend to make that mistake.)
I don't know whether any sort of god exists, and I tend to doubt it. But, the god I don't believe in is definitely not petty.