Yes it is a bit of a problem.
Someone here told me a couple of days ago that flagging cost you SP as well as upvoting...
But it is irritating indeed.
The whole idea with this new concept, a blog platform on a blockchain, is also that posts on the system are impossible to remove afterwards....
So these spam or irrelevent postings will stay endless....
It would be a good idea if there was more space on top of your homepage here on steemit so that you could place a warning message, like the one in your posting, on the top of your page.