Too much presale discounts will be bad for main sale investors.
why do you think so? it might attract other investors imo
Well, he got a point. When there is a huge bonus, the ones who invested in the pre-sale tend to dump their tokens when they can get some profit which drives the price down below the ICO price. So if you look at the price as an investor of the main ICO you will ask yourself, why you paid the ICO price and not bought off an exchange.
In simple terms it averages the price of the tokens down.
Any higher price comes from speculation on future value or a deflationary mechanism in the token.