Try saying, at least to yourself, "What about that statement ITSELF" any time you hear these grandiose "Who is to judge?", "No one can know THE truth", "Everything's relative" types of philosophical claims and questions.
"What about that statement itself?"
is one the most important questions in philosophy, especially for non-philosophical individuals.
It can make a lot of lights go on, and turn the tables in many situations. The statement
"No one can know the truth" ---is paraded around like that statement itself is the truth, isn't it?
See? You're becoming a streetwise philosopher already!
I have seen non-philosophical people of all ages have eureka moments, even turning points in their lives, just from thinking about this one almost magic question.