This is unreasonable to me when both possible worldviews make such wide-reaching claims about reality, and require me to subscribe to particular rules and philosophies--especially when you consider these beliefs are in direct opposition to one another.
As the Christian god demands "You shall have no other gods before me" how can I freely consider participating in other religions alongside Christianity? Surely one of them must be closest to reality with its claims--unless I am to regard the demands these religions make of me merely as suggestions, or allegorical teachings? While that's certainly possible (and, I'm told, the case of the Greek and Roman gods), that's not how I often encounter religion in my life.
Typically it's being cited as edicts or prohibitions that must be followed, lest terrible things happen, and being used to motivate people's decisions around policy and behavior, policy and behavior which I've watched cause harm to myself and those I care about.
I find it a ridiculous proposition that a person could make a decision that would have such effects by seeing which of these contradictory things "resonates" with them, somehow.