Operator Error?

Letter in paper this week:

Sir - I recently attended N***e hospital for a pre-operation assessment. Imagine my horror on passing reception and seeing a poster declaring "Thieves operate in this area".
I had rather hoped to have a surgeon operate.
Yours etc.

Next day follow-up letter:

Sir - N***e hospital is fortunate to have thieves operating. At my local hospital is the notice "Guard dogs operate here".
Yours etc.