The idea that corporal punishment is effective is not the only valid point those of us who support corporal punishment have. have written thousands of words on this forum outlining numerous reasons why I support the availability of corporal punishment in schools. The fact it is effective is only one of those reasons. You are entirely at liberty to choose not to respond to what I write if you wish but do not misrepresent what people have said.
But, yes, one of the big arguments in favour of corporal punishment being available is that it is effective in some cases. Would you prefer people only argued for ineffective methods to be used. The bottom line is that efficacy should be at the core of anything done in schools.