i dont agree on the part that bitcoin has no practical use but i somehow agree on the part that bitcoin could be damaging to the economy . 

bitcoin do have practical use and that is for paying , buying , for investing , trading , etc... 

bitcoin could be damaging to the economy in the form of bitcoin mining where too much heat is released from mining hardware  . bitcoin can also damage the economy if bitcoin is used in a wrong way due to its anonimity feature  where you cant be easily traced if you'v done something wrong  .