Hi Taka,
Men should have created religions, which can/could teach the values that are/were different from those of ordinary people. Now such religions sometimes become the reason of conflicts.
About the parts in red, which tense would you choose? Or are they both grammatically acceptable?
I find the whole paragraph unsatisfactory.
eg the values why is this definite article used?
eg should have created suggests these religions were not created. So how can such religions then become the reason of conflicts?
eg I also question the purpose of the comma after religions.
[ I would prefer 'reason for', although I don't think 'of' interferes with the meaning. ]
I think clarification is needed before your question can be properly answered.
Best wishes, Clive