Strongly seconded. You wouldn't treat your clients with contempt, and you shouldn't treat their clients with contempt.

People use services to solve problems. Some problems demand that level of focus to get it right fast. If you don't take their wants/needs seriously, why would they take you seriously? They are paying you, not the other way around, (and even in that case, it's a bad idea to treat people like that).

I see what you're trying to do, but it's coming across as "if you wear a tie and need it right and right now, you're an uptight jerk". Perhaps they are, perhaps they're not, but you're doing yourself no favors by pointing it out.

Also note that people with those requirements are the most likely to pay a lot for satisfaction; they might be the most profitable segment of your client's customer base.