One way public discourse becomes dishonest is when speakers deploy or demand different standards of evidence for truth claims they agree with and those they reject. There is a temptation to see almost anything as sufficient evidence for a position that we either already endorse or would like to endorse. Conversely, we tend to have a much higher standard of evidence for positions that we oppose.
In reviewing the work of David Irving–who is most famous for his being a Holocaust denier–Deborah Lipstadt captures the point:
“[Irving] demands ‘absolute documentary proof’ when it comes to proving the Germans guilty, but he relies on highly circumstantial evidence to condemn the Allies. This is an accurate description not only of Irving’s tactics, but of those of deniers in general.”