If the work is impactful and worthy of publication, submit it to another journal and watch the citations soar over the years, if number of citations exceed those of the iniital journal the work was rejected from, it's their loss.
Béla Vizvári , I understand your concern. Journal editors do behave unethically. Many rational explanations can be given to justify and support their behavior, but only victims understand the cruelty done against them. I have also experienced similar things that you have experienced, and probably all researchers experience this cruelty. Yes, we can not exclude any single of them, in any field of research. All of us are victims to some extent. Let's accept and learn from the experience and be hopeful and confident about our work.