NRomanoff
And dojo I genuinely do think so. Because that person may alienate people. Some may feel he is including them some may not.
I appreciate that you think that it would be worth telling him - for me it wouldn't have been, which is why I didn't. I didn't consider it my job to help him avoid alienating other people, so if others felt like you about it and wanted to point out how boring his conversation was then I assume they would have done, but in terms of his general approach to life, I took the view that it was his problem, and for the most part, his friends outside work did just talk about football, so I assume he was generally fine with his approach.
I would make it clear I don't like foot ball, and the gently tell him if he carried on. I would feel alienated if he kept trying to talk to me about something I had no clue about.
I didn't feel alienated - I knew that he was trying to include me in a conversation and I appreciated that, even though I had no interest in the topic. His was a small world - he had actually said to me outright that he didn't understand half of what I said when we tried to discuss other things as he had no interest in current affairs, music or even the same TV programmes as me. We were inherently incompatible people, but it was neither of our faults, so I did what I could to make our working relationship the least awkward I could.
Why is it ok for him to do that?
Because there was no malice, no bad intention and no other alternative other than never having a conversation with the person who sat opposite me for 8 hours a day! I wanted to make life easier for both of us, and I judged that it was easier for me to suck up some boring football chat than for him to develop an interest in other subjects.
FWIW, since the whole debate has gone a bit meta - I took our discourse to be of fairly neutral tone and have answered your questions in the spirit which I assumed they were intended - of my furthering your understanding of how and why people work within the social constructs, whilst you gave your perspective on how confusing and pointless it all seems to you!
I hope that my answers have been as enlightening as I have found your questions, and even if we don't agree on how things should work, I do understand that the nuances of social discourse are hugely complex and can seem completely impenetrable, although I do think that there is some underlying logic to them if you know where to look! 