Learned to stop topping crape myrtles after watching a 3-year difference on a job in Raleigh
Client had two in her front yard, one topped by the previous crew and one left alone, and today the topped one is a knuckled mess of weak shoots while the untouched one is a single clean trunk. Anyone else had luck talking homeowners out of it, or do you just show them the before and after photos?
Showing photos usually does the trick but some folks still won't budge until you tell them how much it costs them later. A topped crape turns into a weak mess that drops limbs every storm, so when you lay out the cost of cleanup and repeat pruning versus one easy trim a year, they start listening. You can also point out that the shoots grow back twice as fast and never get thick enough to hold weight, which means the tree stays ugly for good. If they really push back, tell them to wait one season and watch it themselves, the tree will make your case better than you can. I've had good luck offering to leave one alone as a test on their own yard, it's way easier than arguing.