From a great number of people's reports about their experiences while using psychedelics, they all seem to follow a common theme (things about opening their mind to God, communing with the great underlying themes of life, opening previously locked doors in their minds). If a plurality of people report having the same experience, then to me, that validates it.

Then there's the solipsist point of view, which is to say, it doesn't matter that someone else thinks you are deluding yourself, because all that is knowable is in your own mind, so you aren't capable of validating anything anyway.

Either way, the experience is validated, to one's self or to the world.