They aren't leftists. They are just idiots. There's idiots on all sides though.
Sorry KK but no. This goes to the fundamental differences between those who gravitate to the left and those who gravitate to the right. It is a very foundational question about worldviews.
The left is much more likely to have thought about it and still say "Truth is relative". They are also more likely to believe that the ends justify the beliefs and that there are no objective, transcendant moral truths.
Therefore "facts" or consistency are NOT a requirement. A story fabricated about Bush's NG service gets full press coverage. Obama's 20 year relationship with Wright gets dismissed and anyone who would dare detail Wrights teachings will be declared a racist. The mere suggestion that the GOP might have poll watchers that make minority voters uncomfortable pours through every news outlet as potential voter intimidation. The very real story about New Black Panther polling place intimidation is minimized.
Can you demonstrate that this is a 50-50, "both sides do it all the time" type of thing with direct examples?
The last great liberal politician with integrity (Patrick Moynihan) once said "Everyone is entitled to his own opinions but not his own facts." Modern liberals no longer believe that.