There is a lot of scientific self-deception about – and not only among ideologically motivated activists who wish to opportunistically use science in their campaigns.
Scientists themselves are also prone to self-deception – as Richard Feynman sums it up the meme displayed above.
I like this cartoon Eureka! with Regina Nuzzo from Cara Gormally as it indicates why we are so prone to self-deception and some things we can do it overcome it.