These days when Muslims give advise or denounce an unislamic act publicly done by a fellow Muslim, some Muslims will say “ who are you to judge them? only God can judge them” the Sahabas R.A when advised to fear Allah, will thank the person with tears in their eyes.
"O you who believe! Stand out firmly for justice, as witnesses to Allah, even as against yourselves, or your parents, or your kin, and whether it be (against) rich or poor”
"Whosoever leaves off obedience &separates from the Jamaa'ah & dies, he dies a death of jaahiliyyah. Whoever fights under the banner of the blind, becoming angry for 'asabiyyah (nationalism/tribalism/partisanship) or calling to 'asabiyyah, or assisting ...
Because Allah tells us to, Let there arise out of you a group of people inviting to all that is good (Islam), enjoining Al-Ma‘roof (i.e. Islamic Monotheism and all that Islam orders one to do) and forbidding Al-Munkar
I heard Allah’s Messenger (ﷺ) say, “When people see something objectionable and do not change it, Allah will soon include them all in His punishment. (Al-Tirmidhi)
If you see a munkar (un-islamic act), you change it with your hand; and if you cannot do that, then change it with your mouth (speak out against it); and if you cannot do [even] that, then forbid it in your heart — and that is the least of belief. (Muslim)
Verily, in the time of the Prophet(ﷺ) the people would be judged by revelation, but the revelation has ended. Now we judge you according to your outward deeds.
(al-Silsilah al-Saheehah by al-Albaani, no. 2598)
guide us all ameen