I teach danish, history, religion & nature/science.
I rarely trash anything (though we saw a documentary on human rights in Saudi Arabia and it was impossible to defend what is happening there), but I point out what can seem odd from an average danish perspective and try to discuss other perspectives.
Like Creationist vs Big Bang Theory - we discuss if both things can be true.
There was a Big Bang, and it has been proven through observations and calculations, but you can believe it was caused by a divine force etc.
Also notes that many scientists have been religious and how religious people can fuse science with faith, if they are willing to take into account that some holy texts were (wrongful) guesswork, but that it is still reasonable to hold on to the general idea of religion, if you can accept that not every "holy" word should be taken literally - like the World is only 6000 years old.
So - to make room for most peoples standpoint.
Also keep in mind: You can explain and understand many things, but that is not the same as excusing them. (Like the german anger after ww1 explains how nazis could come to power, but doesn´t excuse it or its consequences.)