Discussing, especially online or in politics, is often not for convincing your conversation partner, but for convincing the silent readers. I feel like this objective is more easily reached if you always assume good faith arguments.
I agree with first part but not with second. If you recognize bad faith argument and treat it as such, you can show why it is bad faith. If you don't recognize it that way, you will argue circles or leave implied lies unaddressed.
But, when the discussion is actually in bad faith, you wont solve the issue by pretending to yourself that it was in good faith.