Non-acceptance results in suffering.
But some things are totally unacceptable!
You will never be able to fully accept anything that you perceive as totally unacceptable.
Stop trying - it is impossible.
But you can accept that you cannot accept. This calms down the reactivity and takes you away from mind-based suffering.
Then, if you can do something about what you cannot accept - do it!
But if you can't - accept that you can't. Accept deeply, at the core of your being, and you may find that peace emerges from the depths of our consciousness to envelop the unacceptable.