Maybe, it is not a perfect timing to buy when there is a panic selling. If you will based upon the technical analysis, once the support will be broken, there is a tendency that the support will become the resistance. Once you bought during a crash, you may loss a lot specially, if you during the first crash.

Aside from that, there are always good for being a panic seller than always hoping for the correction of the market. As I know that the market discounts everything, when the market is at the downtrend position, don't assume that it will break the top. Therefore, panic selling is also a safest way of trading.