Well, a not unexpected muddle of thinking by a non-expert but a disappointing level of thought for a government minister. Presumably, civil servants and colleagues are giving him enough rope to hang himself with or are too busy with Brexit to notice or care?
Firstly, one is a primarily commercial structure likely to be rebuilt or remodelled to meet other needs within another generation. The other a government institution intended and budgeted to last 200 years or more.
Secondly, the Greek tradition was raised from the dead during the mid-C18th Enlightenment as a challenge to the baroque tastes of absolute monarchy. At first, resisted for its plain and ugly repetition to what we think today as 'organic medieval accretions' it took a generation of learning to acquire its taste by conflating it with enlightened thinking before being accepted. Independent America adopted it with vigour as you would expect, Europe later with its revolutions. It's still a matter of learned tastes at the end of the day.
Perhaps we're seeing the first steps of the Ministry of Taste with specialist advisors Roger Scruton et al? Like multiculturalism, you can't pretend it doesn't exist or try and crush it out of immigrants. Indeed as the worst of right-wing thinking fears alternative ideas infect our somewhat deluded sense fo purity and we tend to be the better for it. Some are no doubt confused and concerned, it's for those in a position of responsibility to have an outlook that can appreciate a plural world, where and how design can best be applied. Not make ill-founded comparisons to judge what is "degenerate art and architecture".