You are talking about takfir right? I did NOT do takfir since I did NOT called any
individual muslim kafir. I talked about a group and ideology and I talked in generality. Example - those who believe in trinity are kafir, those who worship idols are kafir, those who believe in secularism are kafir etc. Also suppose someone publicly says he is a hindu then it would be natural for me to consider him a hindu. Its NOT judging.
Look if someone says he is a Muslim its imperative on me to treat him as a muslim unless he shows (by his actions & words) otherwise.
As for the imam you are mentioning I do not know what he said BUT yes you can judge. In islamic history jurist always judges in matters such as apostasy and blashphemy and did takfir on heretics. islamic jurist can judge. But yes takfir is a serious matter and common Muslims better NOT do takfir on individuals ....unless that individual's hereticism and blashphemy is clear cut. Its only the domain of Islamic scholars and jurist.
I did NOT do takfir on anyone.
Please here are some materials you can read about takfir :
https://islamqa.info/en/85102
https://islamqa.info/en/6688