Because right-wingers say so - that's why.
How often do you hear one or another variation of the message that liberals are bad and conservatives are good? And how often do you hear messages that counter that? Right. That is because one side is marketing a viewpoint, and the other is not.At the right-wing Townhall.com, Why liberals love pedophiles
The guy tells a story about some pedophile no one has ever heard of, and turns it into a lesson about liberals being immoral. So let's learn from this. Let's look at how movement conservatives do it. They "always add the because". They tie every small story to a larger ideological lesson - a strategic narrative.
"Since modern liberalism's true goal is the actual eradication of God, moral values, and the ideas of absolute right vs. wrong, it should surprise no one that not a single leftist politician in America has denounced [pedohile no one has ever heard of]. Nor did they denounce [pedohile no one has ever heard of]. The truth is liberals seek sexual utopia where no rules apply. Restraint has in fact become a dirty word to them. Self control - a throughly foreign concept.
... For liberals to denounce pedophiles, ultimately they would have to denounce, lesbianism, homsexuality, and their particular favorite - adultery. And that's just no going to happen.
At the end of the day there are such a thing as moral values, and liberals despise them - because as they see it - those moral values limit their sexual freedoms. And if this is "America" - isn't it all about the freedom to get your groove on?
Liberals love pedophiles.
Isn't it shameful?
And don't we all wish - that they loved the well being of children more?"
But here's the thing. They have that strategic narrative in place to tie their stories to, even if they have to fall back on the old basic one - conservatives are good and liberals are bad. So they have a ready-to-go angle to use with any story that comes along. And they understand the basic marketing reasons to do this. Progressives don't. (Is that because progressives are bad and conservatives are good?)