When you disable a plugin via UI Jenkins doesn't check its dependant plugins via Java. 

To avoid disabling a plugin with dependant plugins, Jenkins disable the checkbox in the Enabled column in the Plugin Manager. But if you enable it, via Developer tools in your browser, you can disable this plugin, leaving the dependant plugins enabled and an inconsistent environment.

If you restart Jenkins, a message is showed warning about that.

It could be interesting to check the dependencies in the disable method in Java: https://github.com/jenkinsci/jenkins/blob/caf3e0808906929d52105dca4af197c569270a38/core/src/main/java/hudson/PluginWrapper.java#L524

Doing it, the UI, CLI command, API and so on can truly rely on this method, not having to do this check in every place.

It was found working on JENKINS-27177