And the second, tax doesn't protect anything from fraud...
Look at the bright side, if you have fallen for a sam you can claim those as expenses to reduce the tax you pay on your profit

if the project is scam they will get penalty or delisted/banned from their country.
Yeah right, so how does this help you?
Once a thing is proven to be a scam it means investors have lost money, banning it from the country or delisting means zero chances of ever getting a penny back, the only thing a government could do is try and seize assets but usually, it's always too late.
When the market is taxed, that means it's regulated and the government will impose a penalty on those who are running a scam project.
Impose a penalty?
How is going the government of India impose a penalty on things like bitconnect?
I just love it, for years people are saying how cryptocurrencies are out of reach of the government's regulations and now suddenly the government can issue a "penalty" on those running a crypto project.
So which is it?