Don't even try. Trying to convince someone in a straightforward fact based approach only works on someone who comes looking for that information. Bringing it to someone who isn't looking for it causes them to dig in even further, it is not a rational behavior and can't be dealt with rationally either. This is not a dig at these peoples position either, for all I care they are in the right here. People are not Vulcans expected to rationalize every aspect of their lives.