"He also said the $50,000 threshold is too low and could hurt businesses that are aiming to grow."

Too low???? How much money do you have to have sitting there earning passive income to make more than $50k a year? Assuming a (really) good passive rate of return of 7%, you'd have $718,285.71 sitting inside a corporation earning passive income. That's at 7% - if you've got "safe" passive investments, then you're capital requirements will be higher ($1 million at 5% or $1.667 at 3%)

If you have a corporation that is engaged in active business activities and you've got $720k sitting inside of it not actively working towards your core business, then you're rich. The $50k limit is too high and should be lowered to $15k ($215k earning passive income at 7%), or maybe even $10k ($143k at 7%).

Anything above $15k in passive income should be taxed at the stupid high rate, (or of course, it could be salaried/bonused/dividend-ed out and taxed at personal rates).