Why is something biased whenever you disagree with its conclusions?

Maybe Oswald just acted alone.

I have yet to see any compelling evidence to contradict this. A whole cottage industry of of kooks and amateur investigators continue to feed into the bizarre need some people have to believe in a conspiracy in this case (and absolute refusal to accept any other possible scenerio having taken place). But it doesn't change the fact that all the evidence points to Oswald being the murderer of JFK.

Some people use evidence to inform their opinion. Others use their opinions to inform them which evidence they consider to be "biased" or not.