You mean an additional tax after the mining fees. These things will affect the mass adoption of bitcoins as a payment system negatively. With so much tax on each transaction, people will simple move to alternative payment mediums that have less tax. Also, bitcoin transactions should not be taxed by government as government has played no role in the development of bitcoins. They do not have the right to collect tax on these transactions. However, I think that tax on bitcoin profit is fine otherwise we will see criminals and corrupt people spending all their money in crypto.