Paul, I know you said we only take the **** of the occasional car whereas their site is dedicated to doing it, but even if we had only ever done it once that would still make any person that had posted sarcastic comments on that thread and then made similar comments about Barryboys hippocrits. I have made comments on a couple of those threads, fortunately I haven't commented about Barryboys, but I'm sure there are some that have done both.
As far as copyright is concerned, yes you need to seek approval of the owner of the photo. That is not necessarily the person who put it on the internet, it is the person who took the original photo, unless of course they have sold they copyrights or they took the picture on behalf of a company or establishment who own the copyright.
If an effort has been made to contact the owner of the copyright and there has been no response, you can get away with posting the picture, if you have evidence that contact has been made. That does not make it legal, but you would get away with it. If the owner then asks for removal of the material, it is regarded as response to the initial contact and must be abided by.