I've had this happen on occasion but for the most part, both teams realize that my strike zone is consistant for both teams and they quiet down but the other night I was
this close to tossing a guy that kept saying the pitches were too high and I needed to call those "illegal". He was chirping from the dugout so I went and asked him if he had a tape measure with him, he said no and I told him we would be going by my 12', not yours.
That sat him down and shut him up. My luck, he'll come to the next game with a tape and try and measure pitches. The thing is, most people don't know how high 12' really is. They're not used to seeing pitches that high and when they do, they think they're too high. We've used that 6 and 12' string jig to help us with our height judgements so I have a pretty good idea what 12' is. Not only that, I use a tape measure every day at my other job.