I recently had a plugin on one of my blogs add its own Open Graph meta tags when I already had another plugin provide them. It broke my sharing ability and looked awful (double titles).
The conflicting plugin which I won't name (Jetpack) doesn't allow the user to turn off the Open Graph meta tags it provides.
Plugin authors shouldn't assume their plugin is the only one and realize that OG tags can conflict causing issues.
Yoast's SEO plugin allows me to turn off the OG tags it provides and that is how all plugins with those tags should work