Do you guys have an argument why this is a good idea besides "muh taxes"?
Good, there shouldn't be a national sales tax while there is a national income tax. Pick one or the other.
This isn't a national sales tax. It would essentially just make online retailers pay the full state sales tax.
Internet retailers already pay state sales tax if the transaction is within the state anyway. For example, if you live in Washington State and buy a game on Steam, since Steam is in WA, you get charged sales tax.