Its a fact I will prove it below.Opinion.
Your belief is absurd because it is proven wrong. You believe everyday is bisexual, i am not. If i believed i was a purple flying elephant would I be right?I said I believe everybody is bisexual. I said I believe we all are bisexual. After saying it once, I may have omitted it from any following statements to you. And that may be the reason why you think I am trying to state my beliefs as fact. Sorry. I will try harder to always include phrases like "in my opinion such-in-such, i believe such-in-such.
You can put any prefix in front of an absurd statement out doesn't make it less absurd.
But you also have another way around this, you believe that someone doesn't know their sexuality as well as you do. This is far more absurd than believing in purple flying elephants. You believe you are omnipotent this is more than absurd it's delusional. To believe your labels for people are more correct than the orientation of others, that borders on narcissistic psychosis.