I can honestly say that I have issued far more warnings to people I feel friendly about, and edited/deleted far more messages written by those people, than forum members I have disliked.
Just because you're only aware of the warnings you have received yourself does not mean other people have not received warnings, including people who might surprise you.
The difference is that if I feel somebody is a good contributor to the forum, and a reasonable person, I have found almost 100% of the time they understand the warning or the edit/deletion of their post, and they have tried to improve and play by the rules. I think this is simply about being a "good citizen" and trying to respect the rest of the group, and realizing that we all make a mistake sometimes.
When a person is constantly arguing that they are being persecuted, or treated unfairly, or repeatedly fighting against the moderators or implying we're being unfair, that indicates to me a person who does not care about respecting a community and is entirely about their own interests and preferences.
A community is larger than any single member, and any single member who thinks the entire community should change to fit their preferences is certain to end up disappointed.