Everyone must agree? It's a feeling that envelops you. When you give an opinion to your friends, give a presentation in a university class or office, or give advice to your family.
The answer is NO!
Not everyone has to agree with your opinion. Although you may be right, everyone's ability to think and understand is different. If someone questions you, denies what you say or tells you that what you say has no weight.
So don't be upset, angry or sad to hear this. That's what happens. Not everyone has the same ability to think and understand. So whenever you give an opinion, lecture or presentation. Have your say and lock it.
Now listen to whatever feedback comes and if it is constructive, open the lock and put it in. And if negative, throw it in the trash. Don't let your emotions get in the way. Give yourself love, don't get in trouble or sadness.