I had no intention of saying anything nasty when I mentioned that I think colonics may possibly be harmful. If you don't want to express a dissenting opinion - though you have expressed a dissenting opinion about those who choose to give dissenting opinions - that is certainly your choice.
As for me, if I hear something that I think might be harmful to people then I want to put in my 2 cents. Each person can, of course, make up his or her own mind from all the info available.
Wanting to alert people to a possible danger - as for ex. telling about my friend who felt wiped out by colonics - isn't being nasty but being concerned.