The tweets say that pure math is an important part of the ecosystem of scholarship at a university (slight paraphrase) and I agree with that. I don't really have any concern about axing medieval literature though.
The only people who should be axed are the administrative windbags and "bottom-line" scallywags. So clever, aren't they? I am sure they can survive out in their precious "real world" that they are so infatuated with and sneer others about.
(Besides Sir Michael Atiyah, Leicester also had my favourite topologist, Roy O. Davies, who wrote one of the strangest papers I have read, "Measures not approximable or not specifiable by means of balls".)
(That said, I absolutely agree that administrators should be disposed of first and even if there weren't budget problems.)
Consider if Marks & Spencer announced it would no longer sell clothes, to focus instead on food, for example.
Personally as a math graduate, I think it is better that they focus on areas they are good at. I assume the pure math department is not doing much. It is also good for the students who might want to study math and end up at studying at a university that does not do pure math very well.
Please see my earlier comment. They once had a Fields medalist on their staff. And it was not a one-off coincidence. Leicester has a really good tradition of pure math.