Suppose you worked a job.
Or, suppose you were a student.
Either way, assume you work your ass off. If you don't, you have no reason to complain.
You're paid well, or you receive good grades because of your work. (If you're not paid well for working hard and doing a good job, find a new job. If you work hard and don't get good grades, talk to your prof., get tutored, or take different classes.).
At the conclusion of one year, you have your work evaluation, or you get your final grade for the course. The moment is here! Woot! You're all set to receive your fat reward! Yay!
But your boss/Prof. walks in and says, "Well, look. I've decided to just give everyone a grade of "C" (or rate everyone's performance as "adequate"), instead of having differing standards. Thanks, buh-byeeeeee.
How would you feel, especially if you worked your ass off (see above)?
How do you think the slackers/goof-offs/fuckups at your job/in your class feel?
THAT is what Socialism is all about. Everyone gets a "5" result, no matter if you gave a "10" effort, or a "1" effort.
And (here's the kicker) . . . if you know you're getting a "5" result, no matter what you do . . . how hard are you going to work?