Do you think that maybe everyone is stupid? A little or a lot? All the time, or just once in awhile? I think so, but then, it is raining again., I'm getting married in a few days and I am nervous, my neck is so sore I can barely type and I am generally grouchy. This is how life goes and how opinions form.
We are not always rational or positive or thinking thoughts of springwater purity. Our bad days inform who we are as much as the good days, and often more because I think at the core we hold grudges, and grudges are old hoary beasts that burrow in deep. Grudges are twisted things and any small slights are amplified down in those deep burrows.
That dark stuff can be used! Use it, don't let it cripple you as a person, and certainly not as a writer. You can use everything wherever it may come from and whatever form it takes.