It’s not so much telling him it’s his fault, more advising on easy ways to avoid this kind of thing in future, I’m sure it won’t be the last pothole he comes across…
The reporting procedure is there for cases like this, and if there’s a valid cause for claim then then there is a process to do so, but we also need to recognize that the roads in this country are crap, and sometimes damage appears rather quickly (between inspections) and it’s impossible for every hole to be filled in a timely manner.
The gutters are a terrible place to ride, not just because of holes, but because of drain covers, debris etc. before you even get into discussions about road positioning with regards to overtakes and mixing with other traffic, and personally if I’d hit that pothole and damaged my rim I’d be blaming myself, not the council, no matter how long that hole had been there, but I can see how other people might easily hit it.