But while it's understandable, it's also disingenuous, and perhaps even dangerous. The disingenuity lies in the peculiar notion that being a football fan is somehow determined by moral qualities. As thought it were impossible to be a football fan and a dickhead. As it goes, by many of the more popular standards of footballing fandom properness, those Chelsea fans in Paris were among the most proper fans it's possible to be. They were, at least presumably, the away support, the hardcore, following Chelsea over land and sea.
And the danger? The danger is in the neatness and the patness of what looks like a solution, but isn't. Saying 'they're not fans' might feel like the end of the matter — a personal act of dismissal — but it chimes uncomfortably against the fact that they quite obviously are fans by any metric, and that — even more importantly — they are fans who are happy to simultaneously be fans and be racist, and be both those things loudly and in public.