The Rationalist Judaism blog quotes Rabbi Henkin to this effect, responsa Bnei Vanim 3:18, titled פרסום דברים שאינם לכבוד מי שכתבם:
Rabbi Henkin gives three reasons. His first two don’t always apply. But his third reason is universal and obvious: When someone intentionally publicizes his thoughts, he cannot forbid those who disagree with him from discussing his words with their own thoughts.
[A reader has pointed out that the words “with their own thoughts” are my own interpretation, but not explicit in the original. This is true.]That’s my excuse for half of this site.