Shaykh al-Albāni رحمه الله said:
“The truth is heavy. So, do not make it heavier with your bad manners. I used to believe that the (main) problem in the Ummah is ‘aqīdah, but it became clear to me that it is ‘aqīdah and manners.”
Source: Silsila al-Hudā wa al-Nūr,