Well at least you know enough not to use that farrier if you have/get a horse! Yeah, you see some terrible egs, and it may or may not be necessary to 'bite your tongue' & say nothing. If you know little too, it's more likely to be taken badly... tho often it is anyway! So... you can't fix the world, so choose your 'battles' carefully!
But yeah, if you care about horses it is very difficult to 'turn a blind eye', and I don't personally feel it is right either - if no one will speak up for a horse/practice... As you say, the owner may just be ignorant(I believe that's the case generally with negligence, not that they knowingly allow it), and how can anyone ever learn better if they don't get told that they don't know??
So... of the horses pictured, yes, I'd be concerned enough to comment on the foundered pony at least, and I do appreciate lack of time etc, but I would endeavor to learn a bit about it before bringing it up. lamenessprevention.org & hoofrehab.com are 2 good sources to start with... you can really get 'deep' with the heap of info there, but you should get a better idea of the basic principles without spending too much time.
The other factor is that it's very possible(common in so many areas) that there are few if any really knowledgeable farriers, and this one may be the best of a bad bunch or such. Also consider the 'politics' of that & careful not to 'burn your bridges'...
Best wishes for you & those horses, that it goes well.