Sorry, that is not how a forum works. It is an Arnold thread but you cannot make it so that no other bodybuilding pictures may be posted. People are allowed to post others in comparison. I often see pictures posted of others in a Nasser thread , or a Yates picture in a Coleman thread.
You are perfectly at liberty to post other bodybuilders as well , there are no threads where that does not happen and we have seen all these Arnold pictures before.
The Nasser pictures got many, many views so people are loving them