Read my reply to Kleptoid and try answering the question I posed to him. If people don't even know what the heck LTC is, how can they even perceive reduced scarcity? Because that's essentially what is necessary for price inflation. The person must BELIEVE that the scarcity of BTC is reduced by LTC. That can't happen if they aren't even aware of it.
If person A has never heard of LTC it doesn't change the fact that person B has, bought a billion dollars worth of LTC instead of BTC, so the market cap of BTC is a billion dollars less than it would otherwise have been, making each bitcoin worth a bit less. Inflation. Person A doesn't need to perceive LTC, only person B does. Of course this example assumes person B would buy BTC if LTC didn't exist, but I think that's likely
If a tree falls in the forest then it is only required that someone hear it in order for it to make a sound, not that everyone hears it.