@selzero Try not to make this worse than it really is. I'm not living in the UK, so I'm not too deep into the full political situation there except of what is being reported abroad.
For any individual living in a foreign country, it is really valuable to know the language. It helps understanding the culture of the country you live in. It helps integrating you into the society and makes it easier to get to know more people - like your neighbors. It makes it easier to get a job.
There are a tons of reasons learning the language of the country you want to move to.
For people not doing that, they often end up isolated in the country. If there are many of them, they typically move to live close to each other - which is understandable. But this is where the beginning of frustration grows more quickly, resulting in more segregation and social issues across the whole region slowly grows. Combine that with lack of job possibilities and the crime starts to rise
Language is key to reduce these risks. It's not the solution alone. But to get newcomers to integrate better, language is the first of many steps. And when newcomers gets chance to properly integrate, they have a chance to start contributing back to the community and society.
There are no easy nor simple solutions. There are no quick-fixes here. But it's a large puzzle with many pieces which all need to fit together.
However, f the political goal is to use language knowledge to block immigrants to arrive to UK - I can agree that is highly questionable. But if it is one of more steps to ensure better integration of immigrants in the longer run, it might not be as bad.
Integration is, after all, the most important aspect of a well functional society.