YABU.
When my grandfather remarried, his wife became a British citizen. She barely spoke a word of English. They lived abroad for most of their marriage, but not all. There were legal and practical reasons why she became a British Citizen, rather than because she wanted to 'abuse the state' in anyway.
I bet no one would have questioned this for a second though, due to his profession and her nationality of birth.
He was a pilot, and she was German.
My grandfather, despite living in Germany for many years, only ever learnt the basics of the language too. They were married for over a decade before my grandfather died aged just over 70.
Despite not having a common language it certainly wasn't a problem for them, their entire married life. You couldn't argue she married him for money as she had a very successful career of her own. It wasn't for children (she never had any). It was very clearly for love.
I think it made it easier for things like travel (if you needed an embassy, you only had to contact one, which given his profession was pretty useful).
I think that its beneficial to learn English, and that it should be encouraged, and be a requirement if people want to work here in certain professions such as medicine, which has implications for public safety, that they have a certain level of English - which isn't actually the case for EU nationals (I think they have only just introduced this in medicine thanks to a german doctor killing a patient due to his lack of English). But beyond that, I don't think it should be compulsory.
Compulsory means that there will always be a human element that is neglected, and that people will be caught out by that pesky thing called love.
People tend to have a problem with this as they automatically assume, that people this applies to are people who come from places that are somehow 'lesser' than the UK and it tends to be thought of in turns of arranged marriages or a dodgy marriage. I find that somewhat stereotyped and discriminatory.