When To Draw Conclusions

When is it most appropriate to draw conclusions about the motive of a killer?

Is it to jump to the conclusion that a shooting at a U.S. military base where the Muslim shooter Nidal Malik Hasan was known to be angry at the U.S. military for the wars in Iraq and Afghanistan, argued that Muslim suicide bombings were OK, told friends hours before that he was going to do "good work for god" and shouted "Allahu akbar" when he shot people has Islamist motives?

Or is it to jump to the conclusion that the Tea Party movement in general and Sarah Palin in particular incited a shooting, when there is no evidence that the shooter Jared Lee Loughner had any contact with them or even visited their web sites, no evidence to suggest that he shared their views or cared about their issues and instead had confused rantings about for example how one should burn the American flag (not a popular view among Tea Party activists) and had a similarly confused mix of favorite books that included ideologically incompatible books Mein Kampf, the Communist manifesto and Ayn Rand's We the Living?

In other words, is it most appropriate to "jump to conclusions" in the case where there was overwhelming evidence of his motive or in the case where there was no evidence and in fact some evidence that directly contradicted the conclusions?

Any rational person would say that it is appropriate in the first case and inappropriate in the second case. But as Byron York notes, the left-wing media absurdely has the opposite view.