The harm to a live conversation of talking over someone is clear. There is no harm here, only a digression that can be ignored or not as participants wish. The OP had as much time and space to make their case. Again, threaded forums are not live, linear conversations, and have different characteristics for what is healthy and useful. Replies, even contradictory ones, are not interruptions. There is not one conversation going on, but many, and the conversation cannot be steered unilaterally without agreement from others to not engage in the original conversation.

In general, there is nothing wrong with detracting from someone's point (though there can be in specific instances). The point may be ridiculous and need detracting!

There is also nothing wrong with being derogatory when appropriate. Some speech is indeed bad and should be called out -- were you not doing just that? (Though I, of course disagree that the speech you were objecting was in any way bad).