Whether the issues brought up are valid or not, nobody is there addressing them.
Of course you shouldn't hold money in an exchange, but you have to put it there first, and that in itself is risky. Ask anyone who had funds in BTC-E when it disappeared out of nowhere. Or of course MTGOX
and any of the other scammy fly-by-night exchanges or ones that got hacked and ripped off.
Sure a lot of these people were stupidly just leaving cash in there, but a lot were trading, and they lost everything.