To some extent, forklifts occasionally passing within inches of fixed obstacles is just the nature of the beast and is not inherently unsafe as long as the operator slows down appropriately and keeps all body parts inside the operator cage.
The more likely side effects of too many tight spaces is poor productivity and damage to product, equipment, and facilities. Since business generally place a higher priority on these than they do on safety, you'd be better off using these as an argument for more space or less stuff.
Your other comment about lift trucks and pedestrians in confined spaces at the same time is much more alarming. Though I'm not sure of specific standards, I'd be rather uncomfortable with a standard-sized lift truck and a pedestrian passing at the same time through any space that is not at least 12 feet wide (and the lift truck better be moving slow). And to be honest, I would look for ways of avoiding that as well. That's just my opinion.