How are we to understand the place of severity and harshness in conduct, and is some people's justification of their harshness by claiming it is similar to the severity of Umar (may Allah be pleased with him) correct?

One of the characteristics of the Holy Quran's cultivation of the believing personality is directing psychological and physical strengths towards their proper channels. For a person embodies love and hate, gentleness and severity, and the Quran directs these attributes to correspond with people's situations, as in the Almighty's saying: "{humble towards the believers, mighty against the disbelievers}" and His saying: "{stern against the disbelievers, merciful among themselves}." Thus, the believer interacts with situations, becoming stern when severity is necessary and gentle when gentleness is required. The Creator did not create humans as absolutely merciful or absolutely stern; rather, He created in them flexibility to adapt to situations. The default for a Muslim is to use gentleness and leniency, and to deviate from it only out of necessity.