If Cano were DF'd, that would at least protect the children in the congregation to some degree. This would be desirable, no?
Answering the question, yes it would be desirable to protect children.
But the sole reason Cano was D-F'ed was that the case was notorious, on all the local TV stations. As I recall, during LDH's "interview" with JR Brown, he (Brown) pretty much said the elders went to the jail cell where Cano was awaiting his bail hearing and D-F'ed him on the spot. Strictly speaking, they broke their own rules, in not announcing it until his 7-day appeal period ran out. It apparently was such a heinous case they wanted to be able to immediately say he was "no longer one of Jehovah's Witnesses".
Do you think he would have been D-F'ed so quickly if the news media weren't involved?
Heck, his victim wasn't even a JW! So, not only were there not 2 witnesses, the one witness would have been a "non-believer". According to the Elder manual, testimony of a non-believer only "may" be considered.
I don't mean to sidetrack the discussion, but the WTS was typically hypocritical in the example you cited.