I don't mind the cross-posting. Most people are just trying to get images seen by more people by doing this. Some people are members of some communities and not others, while other people may be members of the latter communities, but not the former. Cross-posting is a good way to have as many people see their pictures and thoughts as possible.
But if they're posting spam or other advertising things in communities that they know they shouldn't be, apologizing isn't going to help. If the maintainer doesn't want it, then it shouldn't be done. They apologize, and expect that people will forgive them on that basis alone. Personally, I don't mind announcements for other communities. It's a way for us to see that there might be something out there which might interesting and hadn't thought about putting on our interest list or didn't think other people would like to talk about. Some community maintainers don't want this, though; which is fine, because it is their community and they can set the rules.
Okay, time for bed... a little earlier than normal, but I have a massive headache and am really tired.