This wasn't tone-policing, it was tone-neighborhood watch at worst. You can't dismiss an argument because of tone, but you certainly can call someone's attention to how their argument may be interpreted by their tone.

There's no straw-manning going on here. He interpreted (quite sensibly in my opinion) it as a challenge to the father. Regardless if that was intended or not, it was the first-read impression I had as well. Now that the OP has clarified his position, now I know that it was not the intended position. If it were not for the response, none of this would have been clarified.