what i get out of his writing is something along the idea that positive liberty is tyrannical because it opposes the freedom to be irrational - and true freedom should uphold the freedom to be as ridiculous, irrational and absurd as one desires. to begin with, i don't think that is actually true. what he's doing is falsely conflating an authoritarian streak towards forcing "progress" (a good example would be stamping out the ridiculousness of christianity by the sword rather than through education, or the british colonial tradition of assimilating aboriginals.....the roots of which are in the inquisition.) with the idea of positive liberty, and then constructing a strawman to take down advocates with. in truth, if positive liberty is the freedom to be in real control of ourselves then it follows rather clearly that these controlling behaviours are in abrogation of positive liberty - and also that any level of absurdity that can be imagined comes clearly from this ideological starting point. his argument is frankly hard to follow.

but, that isn't really what he's getting at - what he's really getting at is more in the question of sanction. that is, he skips a step and takes a big leap of logic to get there and then comes up with something ridiculous with a clear political motive. the more fundamental point - and the one that is actually cogent - that he's really concerned about is the freedom to be absurd without consequence. he then compresses that together into the unified idea of the freedom to be absurd - which is either irrigorous or, more likely, consciously disingenuous.

the answer to this is in mill, and really any writings by any liberal thinker: to separate what he's slyly compressed. the freedom to be absurd is one thing, and the freedom to be absurd without consequence is another. now, if one is absurd and harms nobody then there is no basis for any kind of action by anybody - individual, state, collective or not. but, if one is absurd and that affects others negatively, it does indeed stand to reason that they should be held liable for it. to conclude that one is not truly free to be absurd if they are to be held liable for the consequences of it is itself absurd.

so, berlin's true argument is really simply that true freedom means that the absurd should not be held liable for their behaviour - even when it affects others. you'll have to excuse me for not taking that particularly seriously.