Depends... if it was busy and they wanted to free up some space then I can understand... if it wasn't that busy with plenty of spare seats then I'd say it's somewhat uncalled for.
this, it's bad business practice, especially if Jonny is a 'semi' regular, look at it this way, if Jonny goes in once a fortnight and he and his partner both have 3 drinks at say £3 each, that's £18, over a year, that's £468, say they eat once a month, there's another £240 over the year, so now that's £708 of business lost in a year.
Everyone in business knows, you're best advertising is word of mouth, and bad publicity spreads a lot more easily than good publicity, so Jonny has told his mates about this bad experience, they may or may not choose to go in there in future, especially if Jonnys mates attend the venue with him normally in the first place.
Now, what harm was Jonny and his partner doing sitting in a quiet corner with ample space for other customers, so what if he wasn't drinking, he normally does, and in this day in age, i don't suppose any business can afford to be throwing money away like that, £708 may not sound a lot to a business, but, believe me, it is, especially for a dying trade.