Because that's all they have?
They believe unequivocally in "the ends justify the means" If the cause is justified, in their mind, any means necessary to achieve it is acceptable. Unfortunately for the rest of us their cause is the destruction of America.
Because that's all they have?
Sure. You lecture at colleges about racism, but have no concrete examples of it, so you vandalize your own car with racial epithets (and end up doing prison time for it). Or you're an anti-christian bigot (even though you're the chair of the religion-studies department at the local college), so you make a phony police report about some good ol' christian boys roughing you up on the side of the road. Or a couple of druggies kill you for drug money, but because you're gay the crime is framed as an anti-gay murder and you're turned into a martyr. Or...
The Lying Left, Then and Now, by Chuck Devore
This is a very good article. Good History. I just saw it in my January 9th Human Events newsweekly.
"Why is is that the left always resorts to lying and cheating?
Because that's all they have?"
Well, yes. But also, why not lie? If you don't believe in God, etc, why not lie?
Viability.
Leftist ideology is underpinned by tenets which are constantly refuted by outcomes of their implementation. This means that lying, pretzel logic, subterfuge, revisionist history, and lately their most valuable tactic, CHANGING THE SUBJECT, are necessary to maintain and propagate.
Leftism rests on emotion, not logic; therefore viability and propagation can be maintained and fostered with mere rhetoric. What they say doesn't have to be true, it just has to be stated in order for the faithful to continue the willfull self-delusion.