I think Bill Gates only sees the bitcoin from the negative side without seeing the positive side of bitcoin. Let's imagine when bitcoin users can really change the world economy even dominate all the currencies. Perhaps Bill Gates will retract his statement.
Before cryptocurrency like bitcoin used by criminals, terrorists, etc. to buy goods, illegal drugs, highly weaponized equipment. Bitcoin before as one of the market hideout for them to continue their illegal activies. But now, bitcoin is purely used in any type of transaction. Bitcoin can be used now for good deeds like sponsoring, donating, buying and selling legally.