If you believe that you have caught your enemy in a contradiction, you are mistaken. At best, you have misjudged their real priorities and goals. At worst, you have fallen for a deliberate smokescreen, designed to confuse and distract you. In a political struggle, there are no “meta” statements — all claims and arguments, including and especially seemingly descriptive statements about goals and priorities, are moves in the game. Take the example of a hard-nosed, zero-sum negotiation: when someone claims something is non-negotiable and later gives way on it, that does not show that they are illogical hypocrites. It shows that they were trying to bluff you. It gives you more information to win out in the negotiation going forward (or tells you you’ve already won).
I have long been a critic of liberal hypocrisy attacks: they say they care about the deficit, but they favor huge unfunded tax cuts; they say they favor gun rights, but don’t stand up for black gun owners; they say they’re pro-life, but abandon millions to die without medical treatment. In reality, liberals should be familiar with the gambit of embracing a seemingly abstract principle while secretly wanting more specific results — see the rhetoric of “diversity,” for instance, which clearly means a particular kind of diversity (racial, gender, sexuality, etc.) and definitely does not mean other kinds (a rich panoply of Nazis, flat-earthers, etc.). Everyone tries to “launder” their particular goals through empty slogans that have broader appeal. The right is willing to call out the smokescreen for what it is — “they say they want diversity, but only their kind of diversity!” — whereas the liberal weirdly insists on holding them to the principle that has just been revealed to be a lie.
And that’s because liberals are mistaken in the most fundamental way: they have not simply misjudged their enemy’s priorities or strategies, they have misjudged the very situation in which they find themselves. They think they are dealing with a debate partner rather than an enemy. I can see the appeal of a world in which there were only debate partners and no enemies, but we do not live in that world. There really are enemies, and they can’t be defeated by tattling to some non-existent judge about how they’re not playing by the rules.
An und für sich 
surely there are more categories between debate partner and enemy, e.g. something like “opponent in negotiations”.
Good general point though. Academics purport to be extremely sophisticated about language but are often shockingly naive about the social context of communication and how it affects language, the ways language is used differently as a tool in different situations, from persuasion to posturing to negotiation. Too many assimilate everything to some kind of denatured debate logic.
Adam go on Chapo !
More substantively, I think the eternal appeal to referees and rules by liberals is another move in the game, with quite the pedigree. Liberalism remains the proverbial end of history as far as mainstream culture is concerned, and as such can naturalize its claims and interests via institutional formations and social rules. The efficacy of decrying hypocrisies in politics is historically contingent on having liberals in positions of power.
If such moves seem to be losing to more emotional ones (“populism” etc.), to me it’s only a function of the creeping loss of confidence in liberalism as a whole. But liberals themselves will not adapt their rhetoric to a populist playing field, just as Ancien Regime figures did not attempt a more liberal rhetoric.