It is precisely the opposite.
Without altcoins, right now, everyone would need ASICs to mine bitcoin. That would drive people away.
Altcoins give people with average or better computers something to mine.
Altcoins get people into cryptocurrency and staying interested in cryptocurrency without a huge investment.
Altcoins provide something for people to speculate on and trade their bitcoins for.
Altcoin values SUPPORT bitcoin, not the other way around.
When bitcoin crashes, altcoin prices also crash. They are tied together directly.
Good points made, but they still STEAL AWAY money that would be invested into bitcoin, were it not for the competition.
In other words, the combined market cap of all Crypto Currencies would be slightly less were it not for the competition, but at the same time, all that money would be in bitcoin instead.
I do agree it may take a bit away from BTC, on the other hand it also opens up a ton more money changing hand indirectly and going into alt coins.