So, as long we disagree on the premises of the reasoning (to me LTC is a all round shitcoin,for you it has validity as "Bitcoin Testbed") , we agree on the consequences (LTC is rubbish).
Well, it's a start!
I don't think there is much disagreement, because your point is valid too simply for the reason that we have a Bitcoin testnet for testing purposes, hence the name. It's just so that Charlie Lee has done a lot to make sure his coin will be the first to run certain implementations to see how they fare with mainnet use. It's a clever way to add some usefulness to Litecoin.
The major aspect that makes Litecoin valuable is its network effect. After by default listing Bitcoin and Ethereum, new exchanges are very likely to list Litecoin. It's too important as property and for that reason can't be ignored.