Remember that Craig's List is read by all kinds of people with all kinds of ideas and personal agendas. It only takes one person with their own agenda to block your ad. Just reword it and keep putting it on there. Sadly, there are a lot of people who have no power or control in their own lives who abuse the power they have to anonymously control you by flagging your ad. There is nothing wrong with a reasonable rehoming fee, almost everybody has one. Whether pet dogs should be bred or not is an issue that should not be settled on CL. Don't get into that debate. Do check out your buyers as you indicated you would. Don't take the flagging personally.....whoever is doing it doesn't even know you.