Is it the most reasonable choice to sell BTC now and turn your attention to other investments?
What actually your goal is? Is choosing now still a profit for you? Because if not, you better wait and let the market do the call on what you must do.
If you hold your Bitcoin for many years (as you've said) then you're already aware that the price currently is just temporary. So if you're selling at the current price, you became a weak investor despite of being a hodler for years. Anyway, it's up to you though since we have our own way of thinking.
Can't blame him for having a weak hand but if he's in need and that's the best and final option that he can do, then there's no other way to discourage him in doing so.