It is dishonest to use different intellectual standards when looking at different religions.
If one were honestly seeking the truth, then one would judge all similar propositions by the same standards. Thus, all religions would be examined with the same set of criteria. Instead, the religious approach their own religion with unshakable faith--immune to all doubt or evidence--while at the same time they regard other religions (even closely related ones) with absolute skepticism, seeking only to find fault and reason to reject it.
Faith and skepticism are not only different, they are polar opposites.
Using faith to judge one version of the god of Abraham while using skepticism when judging other versions of that god (and other gods), is not intellectually honest.
It is, rather, an admission of complete bias. Such an admission would disqualify any judge in any contest.
Even if the believer claims to be ecumenical and have no criticisms of the "other ways of knowing god", you can bet he will approach other supernatural claims with skepticism. Ask if he believes in fairies, leprechauns, genies, or magic carpets. If he still won't be honest about his skepticism, ask if he really gives all these ideas equal credence with his own religion. (Though, if you have to do that, then you are probably dealing with someone who simply will not tell the truth in any event.)