If am to say, their is no stable coin in cryptocurrency. Every coin has its ups and downs in price. You can day trade a coin based on its fundamental and volume. Etherum and bitcoin falls into this category
Unless for someone is looking to day trade USDT/USD which to me does not sound reasonable and it is a whole lot not worth it, considering the movement cannot even be substantial to get any serious profit from it.
However, day trading a coin should depend on each individual as they will always get to understand the market they are trading, how they are going about it and how they are as well minimizing risk. No trade with a potential profit will end up not having its risk and all this has to fashion out.