For unity to exist, tolerance is a minimum requirement, but it's hardly the ideal. Genuine respect and brotherly love is the ideal.
At one point in my life, my children and I needed to live with my mother-in-law and sister-in-law for a season. We had completely different lifestyles. My mother-in-law was very respectful and did her best to show her love for us, but toward the end I could hardly stand to stay in that house because, even though I hardly had any real contact with my sister-in-law, I felt tolerated by her as opposed to loved. We were very different people, so it's actually kinda impressive that we didn't clash more (she was relatively quite tolerant and patient with me), but this was the first time I understood the real difference between tolerance and love.
Tolerance is no ideal when it comes to human relationships. It's putting up with something that either causes pain or which one dislikes. Tolerance can tide us over for a while, such as with strangers, but for any long-term relationship to work, genuine respect and love are needed.
So when people here on the DP are spiteful one with another, it's because their tolerance has run thin without being replaced by respect or brotherly love or appreciation.
For example, I'm a follower of Christ, but I respect and feel a love and appreciation for those who don't believe as I do. I know that they had different life experiences than I had, and I appreciate that they can reach a different set of people than I can. So when I read a post by someone and I don't agree with their worldview, instead of rolling my eyes at their foolishness and decide to tolerate their idiocy for the sake of unity, I acknowledge their right as a human being to have their own opinions, I try to learn from them (if only so I can better understand someone outside of my life experience), and I appreciate that they can talk better with others of similar mindset than I can. They are comrades.
I'm hardly perfect in my own attempts to be loving and respectful, but I do try ^_^;
"Moderation in temper is always a virtue; but moderation in principle is always a vice." -- Thomas Paine