Because you express your opinion in absolutes (emphasis mine).
An absolute statement being: assertion by the author that some fact or idea is absolutely, undeniably true[It is] a totally different person that cannot be explained away with "well, she grew up and changed".
If you make declarative statements like this, expect an appropriate response in kind. When you double-down, so will others, because now you've started a discussion about something specific. It's not an attack, it becomes a debate.