You’ve made an assertion that it is not true - in fact, a very strong assertion. Do you have any argument to back that up?

I know people who do not view themselves as fundamentally tolerant people.

Further, I know people who consider intolerance as a core part of human nature, who would be prefixing their arguments with "everybody knows they are fundamentally intolerant". People who think tolerance is a fake position that people lie to themselves about purely to avoid violence or "ugly truths".

The existence of people like this isn't a position to be taken that needs backing by argument.

The essence of any organised belief system, religious or otherwise, is that some behaviours are virtuous and some are not to be tolerated, the nature of this intolerance may range from scolding to ostracism to execution. Is is this latter thing that is the only variable.