yes its a bad idea if the leaves are still healthy, they produce food for the whole plant. ive done it before though and i still had crappy little buds on the bottom, its just the way they grow. ive heard of tucking leaves out of the way if that works for you, but i havnt tried it. some strains the buds grow along the whole stem others dont. then again someone will probably tell you to go ahead if there was an air flow problem around the plants. clipping leaves certainly wont kill the plant but i guess you have to try both ways and make your own decision.