Just to add a potential twist to the discussion ... we know MK’s songs often have multiple meanings and may be about many stories.
In Scotland, a pint of bitter (ale) is a pint of “heavy”. Similarly, a pint of mild is “light”. It could be why should I buy you a pint of bitter if you won’t get me a mild. Or even drink-wars...why do you drink mild, go for bitter! Or teasing ‘this is a man’s drink’.
Just a thought!
Overall I’d still say it’s a fun tongue in cheek song rather than the ramblings of a grumpy old man!