I find that statement absurd, anything with an effect that powerful should be cherished! Would life be desirable if it were stripped from all emotions, as they too have a powerful effect on the mind? Even if you agreed to that, it wouldn't be feasible as we are biological creatures and not pure rational beings. Denying that our biological self exists, with feelings and all, doesn't solve anything. The spiritual experience you describe is just another part of the human condition, I don't quite believe that 9 out of 10 people on LSD would become preachers, but I see how it can lead to a better understanding of religion. This doesn't require superstition, quite the opposite. When you know that those effects are caused by LSD or substances contained in Mushrooms, ferns or cacti, you don't need a higher power as an explanation for this peculiar state of mind. You might however find yourself coming to conclusions about life that other people on similar states of mind (whether induced by drugs or other means is irrelevant here) had before you, and who used the vehicle of religion to transport them.
So yes, psychedelics, as well as most drugs, should not be taken lightly, but banning them is like razing the Niagara Falls because someone might fall over the edge.