It is true. Some will get to know bitcoin because someone promoted to them an altcoin. Well, it will connect somehow when the person got hooked with the promoted coin. He might also see that there is good with another coins.

It will not make a big difference, but alt coins have helped bitcoin become popular. Altcoins are used to buy bitcoins. Without altcoins, bitcoin prices would go much higher and we would have only option of trading in Bitcoin/US Dollars

I think it would be better and more stable to have no altcoin because of altcoin alot of people are just playing the market.
Playing the market may be positive for them but it can have negative outcomes on the bitcoin price and that makes it less attractive for alot of people.

Bitcoin without altcoin is worse because alot of the attractiveness comes from trading and then if that would be out of the game alot less people would be interested.
If less people are interested then bitcoin will fail and price will fail and it will not get mass adopted which is our goal.

People would probably like using bitcoin without any altcoins because altcoins are nothing without bitcoin but bitcoin along can stay strong, but the only thing that would bother the users is trading will not be available which is a big source of earning profits for bitcoin users.

Just like other things that stand out, Bitcoin will be bitcoin even without altcoins. Bitcoin doesn't need any altcoin, it doesn't depend on any altcoin. On the other hand, all altcoins depend on Bitcoin and without the existence of Bitcoin, altcoin will not be created. Sure that Bitcoin's price is somewhat moved by the investors of altcoins, but that still doesn't mean Bitcoin owe altcoins anything.

And they say they can stand alone. If indeed those altcoin can stand alone it will still be a problem once bitcoin is deleted in the system. How could they gain more users if the biggest one can just fall like that.

Without altcoin, I will not have much bitcoin. I mine altcoin and sell them for bitcoin. I do not mine bitcoin.

any altcoin incrase high to big community bitcoin
you can see history without altcoin bitcoin price is very low
and volume transaction bitcoin is low too

I don't agree, I think Bitcoin owes a lot to altcoins. What you say is true that Bitcoin would still be here even if altcoins didn't exist but it wouldn't be nearly as popular as it is today. It would probably still only have a few thousand users right now. Most people just wouldn't be interested in getting into Bitcoin since the gold rush period is long gone.
New altcoins means new gold rush periods and people want to be early adopters in case the coins take off.
It is simply not possible to dream with Bitcoin anymore. Sure people can say, it will reach $1000's of dollar in the future but deeper down they know they're grasping at straws.
New coins, on the other hand have real chances of making people serious money, they all start out the same way as Bitcoin did, worthless and easy to get but have the potential of reaching the moon. And the altcoin incentive drives people to convert their Dollars to Bitcoin.