As long as it is no illegal in the country where the exchange is operating we will all have to live it it.
But where an exchange is "operating" is up to interpretation. Poloniex and Bittrex operate from the US and serve US customers. Bitfinex is organized in different places (probably to keep the owners out of prison if shit hits the fan), but also serves US customers. Generally this means (to US civil and law enforcement authorities) that an exchange is operating in the USA
I'm not sure if you are quite correct on this
If they see that your IP comes from the US, they ask you whether you are from the US. I'm using a VPN service myself to reach Bitfinex (though I'm not from the US), and once say this warning where I had to confirm that I'm certainly not from the US. I don't know what would happen if you claimed to be from the States. So anyone more knowledgeable is welcome to chime in on this. Regarding the topic raised, all exchanges (regulated and unregulated alike) are using dirty tricks to earn a couple of bucks here and there. Even bigger exchanges like Nasdaq or CBOE had been caught front-running the orders of their clients in the past