Liberal news programs are as likely to criticise liberal leaders as not. Yes, they will criticise conservative leaders more, but that's to be expected.
Conservative news sources, by contrast, are very unlikely to criticise a conservative leader and thus almost all of their criticism is for liberal leaders. Note, for example, that Fox News didn't start speaking out against Trump until he'd obviously lost the presidency, despite his behaviour being egregious by conservative standards in numerous arenas. I also didn't see a single conservative new source that decried the GOP's obstructionist 'never Obama' stance, even when he was attempting to set up single-payer healthcare using a model established by a Republican leader (aka Romneycare), let alone when he was trying to explicitly reach across the aisle.
This is the logical outflow of prioritising authority as a moral foundation. As such, however, it means that conservatives are more likely to overlook or extol immoral behavour depending upon who it is that is exhibiting it. That is a flaw that many conservatives won't acknowledge and I think what Allison was getting at.