There are a million and one ways to get in trouble trying to maintain a lawn in an area with a 365 day growing season, no guarantee of good weather to grow grass or perform applications during that growing season and a DOA waiting to bust someone for not following the label or causing a drift complaint.
I did watch Seinfeld. Remember the episodes with the "soup nazi" quite well. I would have thrown Elaine and George out of my restaurant as well. Being in the service business does not mean your customers have the right to disrespect and mock you. You are their to provide a service/product at a price that enables you to make a living, while providing value to the customer. You are not their to KTA or worse. That would make you a prostitute rather than a lawn care professional.
In the case of the customer you let go, he would have been one I let go a long time ago. If it is bermuda grass, I want to see 1" of water every week be it from rain or irrigation. The irrigation system will be linked to rain sensing equipment if it is an automatic system. I do not want to see it overwatered. Nor do I want to see it dried out. In the case of bermuda, I want it mowed at less than 1" with a reel during the growing season. Especially if it is adequately watered and fertilized. NOT A ROTARY. A rotary set to mow low thins out the bermuda by vacuuming up and chopping off all the stolons trying to take root. A rotary set to cut less than 2" will frequently follow every hole or divot in the lawn, scalping out large areas of bermuda. The first thing to grow back in the scalped areas are weeds. If a lawn is big enough to be mowed with a lawn tractor, it is big enough to be mowed with a 27" reel or a 3 gang mower that can be towed by a lawn tractor. I do not buy into the impracticalities of mowing larger lawns correctly. One of my newer customers had a 3 gang reel mower shipped to Hawaii via air freight. He picked it up at the airport. It costed a little over $1000, but less than $2000 to acquire a mower appropriate for maintaining 1/2 acre of bermuda. Now that lawn is rapidly making progress as far as eliminating goosegrass, crabgrass and various tropical grassy weeds. When that same lawn was being mowed with a rotary, it consisted of at least 50% weedy grasses. Herbicides would knock down the weeds for a while only to have them return. I suspect that mediocre results from applying Celsius or Revolver in residential lawns have something to do with how that lawn is being mowed.
When bermuda or other warm season grasses are entering a period of slow/no growth due to low temperatures/lack of sun, height of cut is to be raised up. It is crazy to scalp bermuda when it is not able to grow back quickly. That just opens up the lawn to weed invasion. The only way out of that one would be to keep the lawn soaked with illegal rates of Simazine applied at illegal times and lots of preemergents.
If a lawn is maintained in such a way that weeds keep on growing, I will quickly run into the annual application limits long before the year is up. Can't ever recall selling digging out weeds or making holes in the lawn with RoundUp. I will also be on the hot seat for lack of results. Sure, I would be willing to lighten up and drop the "soup nazi" act. In return, I am not to be questioned about a lack of results. I am also not to be held liable for violations of the label. My clients and people in the business do know me as the "soup nazi". I would rather have that reputation than that of another clown that either died from cancer or OD'd on drugs. He sold lots of pesticide applications, lawn aerations, Verticut jobs. His reputation was that of a used car salesman that was quick to take people's money to sell treatments. But he did not get the results. I think I am doing something wrong if a lawn under my care needs more applications every year and on top of that needs constant aerations/Verticut operations performed on it. That can only come from improper applications on my part or incorrect irrigation/mowing. This is not about me being insecure. Rather, if I did not know what I was doing and had no integrity, I would sell applications, take the money, allow lawn owners to sabotage themselves, and laugh all the way to the bank. Then I have to look at myself every morning, be able to sleep at night and hope I do not end up in the hot place.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738