Line manager from heaven to hell after expressing interest for career switch

Hi all, just wanting to hear your opinion on this.

Context: Line manager (“A”) has been working for the company for a long time, managing a region but with relatively high turnover. Almost 90% is new to the department.

In the initial stage, A was VERY SATISFIED with my performance. However, things started to change ever since I expressed my interest to rotate to another department. To name a few… change of attitude towards me, hurling nasty comments like concluding that I will be a failure in my career, commenting how I wouldn’t be working on my current job in view of this switch, gossiping behind my back, telling everyone about it…..

I tried to remain as neutral as possible (during our interaction) as we should try to minimise any emotions for such instances…. Minimise any conversation and avoided 1-1/small group lunch unless it’s a team lunch..

How would you have reacted?

P/S, there is no point escalating to A’s boss. P/S, not sure if my future/reputation in the same org will be affected