So far I haven't really engaged with the row about Dubai Ports World buying P&O. Frankly, I don't particularly care about grand icons of British industry changing hands - if you don't think they should be nationalised, it follows that you should welcome that the stock market decides on the allocation of capital between publicly held companies. I don't think P&O should be nationalised, so I really don't care who owns it so long as they are competent (which isn't up to me to decide as I don't own P&O stock).
I also don't think the security of US ports will change very much as a result. The US Customs only search 5 per cent of the containers, after all. But, still...it's fucking Dubai, after all, city of all the scams in the Middle East, next door to the Sharjah Airport Free Zone. And, as Larry Johnson points out, one of DP World's businesses is running the Dubai Free Zone, which is the location of a non-trivial number of firms associated with our, ahem, friend.
However, it's got jack shit to do with inspecting containers or managing the logistics of a big container terminal. It's also true that most of the really sick stuff goes in the other emirates, especially Sharjah, which Dubaians consider a hidebound ultraconservative dump run by Islamic puritans (ironically). It has everything to do with company law, corruption and impunity, which aren't DPW's business but that of the government. If there is a case to block the sale of P&O ports to DPW, it's entirely as a bargaining chip to force changes at home.