I think this will greatly decrease the prices of cryptos.
This few lines got my attention after reading your thread. I have to inform you that tax gives a product or service some legitimacy and the people who are made to pay the tax have some level of confidence in that. So, the move will even get more investors and price will improve better.
The tax payment won't have an affect on the crypto price I believe...
And if investor are willing to pay taxes based on what have they earned then government don't have a reason to ban them on some countries...