The downside is you're following the panicked herd in selling low and buying high. And the items you are buying are going to put even more drag on your portfolio.You and all the terror-prone investors out there are now selling their stocks at deeply discounted prices, sure to drop the prices even further and then either sitting in cash or buying bonds/CDs at inflated prices. This act will cost you way more than just leaving it alone and riding out the fear/panic.
Do you remember the bank panic scene in "It's A Wonderful Life?"
https://www.youtube.com/watch?v=iPkJH6BT7dM"Better to get half than nothing...." If you panic, you sell off everything and you're signing on to working longer just to rebuild back to the level you were at when this started. The bank wasn't going to fail, unless the people made a run and demanded every penny out, but then the guy mentioned Potter was giving 50¢ on the dollar. Why? Potter was buying up bargains because he knew human nature. Panicked people make poor decisions especially when it comes to money.
If you are convinced that flight is the best move, then a less damaging way of going about all this is to leave the current investments where they are, turn off all automatic investing, stop reinvesting dividends (have them put into cash) and all new investing/cash go into bonds or high yield CD/savings. Or at least leave half of it alone if you can.*
I 100% think that doing either of those is a terrible idea, but it's better than the absolutely abysmal suggestion to sell off all your stock positions now.
*you have no idea how much that pains me to write. turning off auto/reinvesting during a crash? That is crazy talk. You're basically saying - "hey I have no interest in the amazing sale prices on this thing I really love!"