Don’t condemn Draco for bullying Harry and then praise the Marauders for bullying Snape.
Don’t condemn Snape for dropping a branch on Petunia at an age when he couldn’t control his magic and then praise Harry for setting a snake on Dudley at an age when he couldn’t control his magic.
Don’t condemn Snape for changing sides when Lily’s life was threatened and then praise Dumbledore, Regulus, and Narcissa for changing sides when the lives of their loved ones were threatened.
Don’t condemn Snape for his treatment of his students and then sweep other teachers’ mistreatments of their students under the rug.
Don’t condemn Snape for being a product of his environment and then excuse various other characters’ behavior by saying that they were products of their environments.
Don’t condemn Snape for doing certain things and then praise other characters for doing the exact same things just because you like them. Your hypocrisy is showing.