[SovietDissident]

Taking morality out of it for the time-being, taxes serve as an additional barrier to entry for smaller companies; these tech giants have hordes of lawyers and accountants to make sure they pay very minimal taxes (if any). These companies are also multinational, so they can keep money overseas and search for tax havens globally---a choice smaller companies don't have.

The point is: you can give big companies whatever rate you want, but they're in the strongest position to circumvent it, and they will. The better choice is to lower taxes substantially and give the smaller companies a chance to accumulate capital faster, so they can compete.