The scholars of the past disagreed constantly and recorded it without contempt. The manners that made this possible are a discipline, not a temperament.
Three classical habits
State the other position in a form its holder would accept. Distinguish an error from sin. Keep the argument about the evidence, and let the person keep their dignity.
Online
A comment thread rewards the opposite of each. Notice the reward and refuse it: reply slowly, quote fully, and leave the conversation before it stops being one.