Meleemaker-Sorry sometimes on forums the members go a tad overboard trying to prove their point or show there knowledge (I know I have in the past, LOL)
Now on to your question....NO you do not NEED a Pleco, but most fish keepers have some bottom feeders to help keep the bottom clean. This can be anything from a pleco, cory, loaches or other types of catfish, this list goes on and on. It really depends on a few things like other inhabitants of the tank, tank size, water parameters substrate and what you want.
I hope this answers your question; if not like Lauraf said, just ask