Personally I am not in favour of sanctioning this type of journalism, simply because it can only increase the exposure of an otherwise irrelevant piece, so I don't find the response particularly disappointing.
Of course I can also see that for people who have the opposite opinion, the above response would be far from satisfactory. So I did a bit of googling (in lieu of actual research

) and came across this article:
http://www.politics.co.uk/blogs/2015/04 ... the-police
It's pretty reasonable, I think, but whether or not you agree with the article, it seems pretty clear that the two things a journalist can be sanctioned for are incitement to violence and incitement to racial hatred (both of these are covered by the IPSO response above). In Scotland it seems as though there is also some incitement law (again, according to inter web rather than actual research):
http://en.jurispedia.org/index.php/Crim ... (Scotland)
In here you can see that:
"A person will be guilty of incitement if it can be shown that he influenced the mind of another person to commit a crime. It is irrelevant whether or not the crime is actually carried out"
They provide this as the source of that - I guess our resident legal eagles would be able to comment further on this!
"Baxter v H.M. Advocate 1998 JC 219; 1997 SCCR 437; 1998 SLT 414"
So from that it would seem if you aren't happy with the IPSO response your next choice would be to attempt to get the author prosecuted for incitement - but to do that you (or, more likely, the police) would have to show that at least one person actually took her seriously and decided that they would go key a sports car (whether or not they actually then do it) - I think you would also have to show that the very same person was unlikely to have done this anyway - i.e. someone with a long list of vandalism convictions is unlikely to be a suitable candidate!
I doubt you would persuade the police that this was worthy of their attention.