I operate on the assumption that leftists are four years old emotionally, and as such they are narcissistic: they perceive things as either all-good or all-bad.
Let's take the leftist hatred of Christianity, which they see as the most horrible thing in the world. Why can they not see what Islam is? Because they can only perceive everything as good or bad, with nothing in-between. So if Christianity is evil ("spook in the sky," etc.) then Islam has to be good.
I think it's just that simple.
Right now leftists are overwhelmingly for open borders ("It's for the children"). But since they can only perceive good or bad, they can flip from one to the other in a heartbeat.
So don't be surprised if they flip from supporting open borders to machine-gunning illegal immigrants...in an instant.
The same applies to their support of anything. Once they get hurt (they can't tolerate any pain) they flip to the other side. Just like that.
And someday they'll support machine-gunning Muslims, too.
To be specific, here are the traits of leftists.
1. Shamelessness: Shame is the feeling that lurks beneath all unhealthy narcissism, and the inability to process shame in healthy ways.
2. Magical thinking: Narcissists see themselves as perfect using distortion and illusion known as magical thinking. They also use projection to dump shame onto others.
3. Arrogance: A narcissist who is feeling deflated may reinflate by diminishing, debasing, or degrading somebody else.
4. Envy: A narcissist may secure a sense of superiority in the face of another person's ability by using contempt to minimize the other person.
5. Entitlement: Narcissists hold unreasonable expectations of particularly favorable treatment and automatic compliance because they consider themselves special. Failure to comply is considered an attack on their superiority, and the perpetrator is considered an 'awkward' or 'difficult' person. Defiance of their will is a narcissistic injury that can trigger narcissistic rage.
6. Exploitation: Can take many forms but always involves the exploitation of others without regard for their feelings or interests. Often the other is in a subservient position where resistance would be difficult or even impossible. Sometimes the subservience is not so much real as assumed.
7. Bad boundaries: Narcissists do not recognize that they have boundaries and that others are separate and are not extensions of themselves. Others either exist to meet their needs or may as well not exist at all. Those who provide narcissistic supply to the narcissist are treated as if they are part of the narcissist and are expected to live up to those expectations. In the mind of a narcissist there is no boundary between self and other.