McMenemy, who managed the Saints from 1973-85, including an FA Cup win over Manchester United in 1976, also questioned whether Mauricio Pochettino had been lined up to take over ahead of the announcement of Adkins' dismissal on Friday.
In his column in the Southern Daily Echo, McMenemy wrote: "Speaking as a manager with more than a little experience - in fact well over 1,000 games at every level from fourth division to internationals - I never get too surprised. But I have to admit that the dismissal of Nigel Adkins and the way it was conducted knocked me back.
"Sir Alex (Ferguson), and you'll get nobody more respected in the world of football, called it `crazy'. Other leading figures have used words like shameful and unforgivable."
McMenemy admitted Pochettino revealed at Friday's press conference that he had been researching Southampton's squad ahead of the announcement that Adkins was leaving.
"At his first press conference the new manager tried to evade the question about when he was first approached for the job but did admit he had been researching the team over the past weeks," wrote McMenemy.
"It will be helpful to him, and believe me he will need as much as he can get, but it really does look bad as those comments seem to suggest that Nigel Adkins was what I can only describe as a dead man walking."
Former Southampton player Matt Le Tissier, who made over 400 appearances for the club, felt Adkins was not given a fair chance after taking the Saints from League One to the Premier League.
A pundit on Sky Sports, Le Tissier told the Soccer Saturday show: "What he has done for the football club in the last couple of seasons meant for me he deserved a fair crack of the whip but he hasn't got it. The team has picked up and there was a real feelgood factor and it just seemed a real crazy time to do it.
"I am not surprised. The rumours have been around at the football club since the summer that (executive chairman) Nicola Cortese didn't want Nigel Adkins in that position. Nigel has just been a sitting duck and that is just incredibly disrespectful to Nigel Adkins after the job that he has done."