There are a few points here. (1) The hatnote at top currently violates WP:RELATED, and ((See also)) shouldn't be used like that. (2) The lead is short and doesn't summarize the main points of the article. (3) This article pretty much overuses ((Main)) (with its use in the section titled "May and Rudd: "Hostile environment" and Windrush" being particularly unwise)
It only discusses the Conservative Party's history with racism through various, but then why not mention their policies. Even if it is a short statement saying their policies have never been explicitly racist, that'd be one thing at least. A political party is much more than the individual leaders.
It represents viewpoints fairly and without editorial bias, giving due weight to each:
This section probably just plainly needs to be cut or heavily re-worked. Apartheid was racist. The people who supported Apartheid were racist. This section does not effectively say Thatcher supported Apartheid (in fact, it says the opposite).
Is it stable?
It does not change significantly from day to day because of an ongoing edit war or content dispute: