I'm not for a moment suggesting that there aren't still racist elements in the fanbase, I think it would be naive to suggest overwise. I think for the vast majority of fan though that really isn't something they believe or follow. If you don't know the connotations of the Yid term though, and you hear Spurs fans proudly singing about being the Yid Army, it certainly makes it a lot more difficult to send a clear message that its an offensive term.With all due respect, that is rubbish.
Perhaps those fans do not know know exactly what they're chanting, it's a real possibility. I'd tend to give Chelsea (and West ham) fans less of the benefit of the doubt than I would a Stoke fan for example , considering those two fanbases are the only two that still occasionally send anti semitic abuse our way (and by anti semitic abuse, I don't just mean singing yid out of context either).
It is of course also disingenuous to equate this with Tottenham fans singing yid and strikes me as (a much milder) form of the same argument about why it's OK for African Americans to say nigger if they get offended by white people saying it.
It goes without saying there is a historical reason (whether you agree with the use of the term now or not) for Spurs fans to associate with the term yid. To cut a long story short, it was historically a word used pejoratively by fans of other clubs based on the assumption that our fanbase was more heavily Jewish than others. To remove the sting from this insult, the fanbase turned it around and took on the term as a source of pride, removing a lot of the viciousness of the term. Bit by bit, other fan bases have stopped using the term, excluding one or two. That is partly down to the changing of football culture in the country as a whole anyway but also partly down to the claiming of that term to be a source of pride.
Having talked to quite a few Jewish spurs fans (and randomly a couple of non spurs Israelis), not a single one of them found the term in this context offensive. On the contrary, they had a sense of pride that the club and its fans had long associated with the local Jewish community. Though I acknowledge that I cannot possibly articulate the general opinion of London or the world's Jewish community.
I'd assume it's also rather clear that the underlying meaning and intent when used by Spurs fan is altogether different compared to when used by Chelsea fans.
You can't use that 'black people use the n word' example because most Spurs fans are not Jewish (I found an online article that put it at 5-10%), so despite the historical links to the Jewish community you shouldn't get any kind of free pass on that, any more than white people who associate with black groups and thinking its ok to use the n word as a result would.
As I said, it doesn't justify other fans using it, but it sure as hell doesn't help. It normalizes it, and makes youngsters who are in a big crowd and hear a chant going around far less likely to understand that what they're singing along with is actually deeply offensive. Hopefully things like the Morata and club statements will go some way to helping educate people, but non-Jewish Spurs fans should cut it out too.