How many times have you heard “I grant your facts and understand your reasoning, but I just don’t see it that way?” That’s the elephant talking!
Another reason is confirmation bias. Psychological research has shown over and over that humans have a tendency to focus on evidence that supports their beliefs and ignore evidence that challenges them. This is why scientists sometimes stick to discredited theories despite clear evidence against them (luckily for us, other scientists work hard to find disconfirming evidence for theories that they oppose).
What can be done?
Here are a few lessons:
It will never be possible to disconnect Israel from US politics, but soon the election will be history. The focus should always be on policies, not personalities. And it is a poor idea to mix Israel with other issues. I once read a persuasive article about why Obama’s policy was anti-Israel, which closed with a negative remark about Obamacare. Stupid.
It is important to be in touch with what is happening on campuses, oppose egregious politicization of supposedly academic activities, and fight to prevent the resources of universities from being used for anti-Israel purposes. Arab and Iranian interests fund departments and programs to serve their interests; Zionists should do the same.
There are numerous organizations opposing bias in the mainstream media. It’s also necessary to develop alternative media, but strongly partisan approaches will not be effective because of the information bubble phenomenon.
Finally, involved arguments about (for example) Israel’s rights under international law are less effective than appeals to fairness, Jewish self-determination, etc.