I'm not having much faith these days in the ability of security in LHR to accurately detect over the limit pilots.
I think we need a little more evidence that said pilot was actually over the limit than simply LHR security pulling him aside. They seem to have difficulty differentiating between the smell of cherry chewing gum and booze....
If he was in fact impaired, have at 'em. There should be zero tolerance in my opinion, and it does the whole profession a disservice when such things happen. But until there is concrete evidence, I'm witholding judgment and assuming the pilot's innocence.