If this guy keeps sending 13 of these spam transactions per block, he will bloat the chain about 1.7mb/day. This might be something we just have to accept. This is the same way that Bitcoin works. If you have free transactions, there will be ways for malicious person to take advantage of it.
Isn't booth Litecoin and Bitcoin pretty doomed anyway unless it is possible to implement a cut-off point for downloading the chain that at least keep the file under a few gig? So, does it really matter in the long run how big the chain gets?
Problem is if you can block real transactions that should have been free by doing this...