^ He never argued that arbitrage is unhealthy. I think you misunderstood his post. He's saying that having multiple BTC-based blockchains doesn't better enable one to take advantage of fiat-BTC arbitrage opportunities.
Ah, his use of the word "combated" leads me to believe otherwise. Seems you're right about the fiat-BTC arbitrage, though. In any case, the BTC/USD rates of e.g. btc-e and vicurex are typically a lot closer than btc-e and mt. gox, presumably because there is alt-chain enabled arbitrage, so hopefully it's a non issue.
Using the word combat was sloppy. My opinion on arbitrage is that when it occurs you should try to profit from it until the imbalances which caused it no longer exist. Hence my use of the word combat.
....... Arbitrage is not a bad thing and is not something that should be combated; arbitrage is healthy in a functioning economy. LTC on Mt. Gox enables easier arbitrage because extracting LTC from Mt. Gox will be considerably faster than extracting USD, and subject to much smaller fees. There are lots of explanations about how arbitrage works. You should find such an explanation and read it. Once you really understand it, it will be obvious why LTC on Mt. Gox will make arbitrage easier (assuming it is quicker and cheaper to move LTC around than USD, which is a fairly safe assumption), and thus the cryptocurrency economy healthier.
As for whether or not LTC or some other alt fills this role, I have no opinion (well, I have one, but it's not really important to the idea of arbitrage).
Can you explain to me how you can use litecoins to speed up the arbitrage trade I discussed bearing in mind that all the historical evidence suggests LTC/BTC rates will be almost the same across all exchanges.