Yes that diluted the overall share of bitcoin in the cryptocurrency 'sector' from say 100% to 99%, but so what. Better a smaller share of a larger pie right?

Any valuable technology sector has multiple actors in it, not just one monopoly. Alts like ltc provide redundancy in case of a catastrophe or an alternative if bitcoin becomes idealogically unsound to some people causing large divides in the community (see the heated debate about Mike Hearn and blacklisting).

Anyone who thinks that the bitcoin community will remain totally in agreement in the future is simply either an idiot or protecting their btc holdings with their fanatically closed minded preaching (a la Goldbugs).

'Just fork bitcoin instead' I hear you cry. That isn't going to work as well. Too much confusion. Also you might get a new power struggle etc with the forking teams. Better to have competing alts in parallel the whole time. Ltc and its highly competent dev team (or someone else) can snap at Bitcoins heels continuously 'keeping them in line' and doing a good honest job.