Student learning is one of the essential requirements of obtaining a degree. That learning starts with the personal standards the professor maintains. This requires day-in and day-out dedication to the needs of students and holding the line even when students grumble. At the end of the day the university wins and the students win.
One thing professors dislike hearing is, "no other professor graded me down for this". Sometimes it may be true while at other times it may not be true. However, the total learning experience is the different grading requirements by different professors.
It is the total educational experience that counts.
Students who deal with different expectations also learn to be adaptable and adjust their learning process to the expectations of the professor. If the professor gives an easy A the students learn to do less work and expect more.
Professors who maintain their standards do the students, the university and other professors a favor. The students learn more by putting forward more effort, the quality of the university rises as the educational standard rises, and other professors obtain the benefit of a more competent student who have high expectations of their own work.