Arbitrage is a matter of market participants knowing what they're buying and selling, not a matter of the shadyness of an exchange.

Also, take these people calling out "arbitrage opportunities" with a grain of salt. Often times there are logistical reasons these gaps in prices exist, and if you try to take advantage of them without limiting your risk, you can end up in a pretty shitty situation.

Source: I used to be a derivatives trader. I've made markets for various cryptocurrencies like Ripple. I know a thing or two about markets.