Partner candidates can acutely pick up on the subtle messaging by the law firm in question on the background to the hire.
So when the Law Firm claim that their most recent defectee to a bigger, better firm is “no great loss, we didn’t like him anyway” let's understand how this will be interpreted by the Partner(s) they are interviewing to replace them. Sour grapes is the short answer. Of course, they will understand that Big City Law is a capricious business so a Rainmaker can be flavour of the month one minute, and persona non grata the next. However, in a highly competitive market for the top talent, the Firms who want to attract the best would do well to acknowledge that realistic, self-reflective and gracious messaging will likely put the dream lateral candidate at ease. Since nothing is forever these days, they will want to know that the firm has an approach to exiting partners that is mature and sensible, otherwise no amount of love bombing on the way in will compensate for a caustic approach to departees.
“He/She served our firm with distinction and will be a loss” can sometimes be harder to say, but it will certainly earn you more respect in the long run.