Politics are pretty ugly. I'd like to be nice and friendly to everyone and work things out well, and I hate to have to distrust people because they would likely have their own agenda. I don't mean that people are terrible monsters that try to make life miserable for you, but more often than not, people have their own ideas of what is right, what they ought to deserve, prejudiced views, self benefits, and lack of understanding of others. All these result in a conflict in agenda and then all these politics come into play and the existence of the initial politics itself makes the politics worse, blowing it up to cold war levels.
Trust, in this case a lack thereof, is the essence. I guess that is why we need to be shrewd as serpents and harmless as doves. I'd prefer if it weren't necessary though.