Connected interview questions

The interview process had total of three rounds. First two rounds were technical and the last round was behavioural. I got the offer. But had to refuse because my old company retained me with a counter offer. Sent a professional email that I will not be able to join explaining the entire situation. Was hoping for a more professional reply saying that if you're looking for an opportunity again we'll be happy to have you onboard. Rather got a rude/unprofessional reply saying that this is a red flag and they won't be hiring me again. Also lots of trash talk about my current employer. After reading that email I was just super glad that I didn't join a company which has this kind of toxic work culture.