Is the feeling of loathing towards someone who left the prayer to go visit a sick person a natural feeling?

May Allah increase your eagerness, but you have gone too far in your hatred for this person. His leaving the congregation is permissible due to his need, and this is one of the things that permit leaving the congregation. The jurists have explicitly stated the permissibility of leaving it for excuses even less significant than what was mentioned. You must assess matters and excuse those whom Allah has excused.