Borrowing money is not a bad thing if you have no other solution and use it for emergencies but borrowing money to invest in crypto, especially trading is a bad idea. Cryptocurrency is a risky market and we will face more risks as a trader, so we should only use idle money or money we can afford to lose, don't borrow money if we don't want to get into bigger trouble.
It is without any doubt a bad idea to be done. Someone who's eager to trade should use their own funds into it because you'll never know how it will end up. Many of the traders that have used their own funds in spending to learn more about trading needs to take their own losses. A borrower being transparent to the lender will get declined once it's said that the money will be used for it and even in investing into crypto. If it's with a established business, it won't be declined but with a volatile market, the lender will have to make sure how the borrower can pay them back.