Rational thinkers out there

Let me be straight and clear because it might be hard to explain and come up with words to explain it.
How do you guys take a side/stand when you have seen the both side of the argument/situation (anything similar to it), and both are correct in their own way. If you take one's side, you know you're not being fair to other one because you can rationalise it and know that other side is also correct. But if you're forced to take one. How do you come to the conclusion.

I always tend to avoid this type of scenario but it eventually happens again. And if you avoid it, people will be left to wonder it they were right or wrong (but you know both sides are right) in the decision/situation/you get the point.

P.S sorry for the bad english