Still I would be against it because it's on revenue not actual net income. Because taxing someone while disregarding total expenses creates artificial debt and many other problems.
All sales taxes are on revenue. Plus, it's paid by the consumer, not businesses.
That aside, an internet sales tax is inevitable and this really shouldn't be that difficult of an issue. However, now is obviously not the time to implement any new taxation- give it at least a year or two.
With that being said, the current bill appears to have holes. First the $500,000 cap for small businesses is too high. It makes it too hard for 'medium sized' (although I don't think most would consider a retailer with $1mil revenues anything but small) businesses to compete with small businesses who don't have to charge sales tax as well as it keeps it difficult to compete with large businesses with their inherent advantages of being big.
Second, if this requires businesses to report and file sales tax with 47 states this will be an absolute administrative nightmare that would be completely unfeasible for any company without a dedicated accounting staff.