I've seen a couple of libertarians sharing the following graphic on Facebook, commenting upon how much sillier it looks a year later now that Donald Trump is the president-elect:
I'm not certain how useful this video is to my general point, but it feels kind-of related: Obama mocking Mitt Romney during the 2012 debates for viewing Russia as the "number-one threat to America":
These are statements which were made with utter confidence by Democrats at the time, which they now are very eager to repudiate. A related phenomenon has been the inflated stature, under Obama of the executive order. Obama has not, by the standards of modern presidents, issued an especially large number of executive orders: indeed, the last president to issue fewer orders during two terms of presidency was Grover Cleveland in the late 19th century. But by using them to cause the enforcement of laws which Congress had rejected, he has prepared the ground for Trump to do whatever he likes, even beyond the probably Democrat landslides in the 2018 midterm elections.
This brings us to a general point, one made frequently by libertarians and classical liberals: that designers of political systems rarely stop to think what will happen if the wrong people are able to take charge of the country. But this is an inevitable fact of politics: democracies elect bad men, great leaders make poor choices of successor, and revolutionary governments are almost by definition founded by men with a taste for violence. This fact is one that we should take into account when setting up our laws and institutions, and there are three basic responses you can give:
(1) The freedom of action of political actors must be severely curtailed, firstly by checks and balances upon what can be done and secondly by limiting the range of actions which any government is able to do, no matter how internally united it may be.
(2) Yes, there are risks to a powerful executive, but they are risks worth taking. There are bad governments, but (at least in the context of a well-functioning liberal democracy) these are very much the exception.
(3) Embrace the hypocrisy, and accept that ultimately what matters is not the meta-level process of how you determine what governments should be able to do but simply what side you are on, i.e. whether these vast powers are being used for a (by your lights) good cause or a bad one.
The people who talk about this problem explicitly seem almost universally to give answer (1). Answer (3) is closer to most people's unconsidered instincts, and I don't actually think it's obviously wrong. (It's uncomfortable for Democrats to oppose Trump doing the very things they championed under Obama, sure, but is it objectively any easier for him merely because Obama did it? I don't know.) I'd be interested to see a defence of (2), which seems to be the option most applicable to the UK.