Is it permissible to adopt the view that water entering the male organ during istinja (ablution after defecation/urination) and then exiting it is excusable, not considered impure, and does not nullify wudu, especially since this view is psychologically comforting?

It appears to be merely a whisper (waswasah), as normal istinja' (washing after relieving oneself) does not usually cause water to enter the inner part of the penis. Therefore, it is advisable to ignore these whispers. However, if you are absolutely certain that water entered the inner part of the private organ and then exited, you must perform istinja' from it because it is impure (najis). The Maliki school of thought has a detailed explanation regarding impurities that exit involuntarily.