Yes...if messy butts caused death by maggot, there would be millions of CX that never made it to the dinner plate.
Fly strike on any livestock is a sign of poor management of feed/soils/pasture/environment...not as a result of a messy butt. Chronic messy butt is a sign of ill health or mismanagement...either way, washing the butt is only a stop gap measure for a much bigger problem.
I'm not surprised at these types of posts when the overall management knowledge on this forum comes from books that advocate crutching an animal's health with the use of dewormers, antibiotics, etc. That knowledge is passed from inexperienced person to inexperienced person as the truth until it becomes the gospel according to Storey and cannot be disputed by a minority of folks like us.
I've found that people who respond to this kind of management really like the drama of having sick animals..it gains them attention. In a world where reality TV rules, folks are bored, have no self respect drawn from accomplishment on their own, and they think that drama is the norm. It's what they respond to....they like having unruly dogs and children so they can have drama in their lives, they like being in debt because it's considered natural now and it also creates drama in their lives, they like having that constant turmoil because they have never learned to appreciate peace and calm.
When was the last time you saw folks watching shows on TV that promote calm, peace, and intelligent action? Nope...gotta be drama, big and dumb action, killing, cussin', and turmoil for it to even catch their eye. Even in books the biggest sellers are mysteries and romances....high drama, unrealistic scenarios, must have turmoil to gain the interest of the reader.