Factual error: Slater had close to a dozen sticks of dynamite on him. At the very least they should have knocked Winona Ryder down, and made her deaf for a few days.
Factual error: After Veronica and JD give Heather the poisoned drink, she falls and shatters the glass table. The way that the glass breaks is not realistic. She doesn't fall far enough to cause the entire top to shatter into tiny pieces. Most likely, the top is strong enough that her body would rest on it.
Answer: He doesn't care if anyone believes it or not; he is trying to make a statement about society and that no matter how we see ourselves in life, we are all the same when we're dead.