One of the trickiest things about being a rookie DM is not being convinced by what might otherwise be a perfectly logical position. It's important to stick to the rules as much as possible until you have a solid understanding of how things work and, more importantly, why they work the way they do.
I used to DM a game with a player who was significantly older than the rest of us (we were just kids at the time) and a lot of his ideas sounded ingenius to us and we looked to him for answers and rarely challenged his experience. Over time, however, we began to realize he wasn't as insightful as we'd given him credit for and by the end of his participation, he was pretty much looked on as a comical figure who didn't know half a tenth as much as what he claimed to know.
It might sound logical that a dispel magic can negate/suppress a construct, but unless there's a rules reference to back it up then be careful b/c there's probably a reason that reference isn't there to be found. (And nerfing every construct with a simple dispel magic is a good example)