It's hard for everyone. I personally have an extremely hard time trying not to think bad of others when I don't even know them.
Please read the following:
He is someone who does A LOT of ibadah. He is frequently seen at the masjid. He has loads of knowledge about Islam. He memorises the Quran a lot. He is very harsh with his friends. He lacks softness when reminding his friends whenever they commit a sin. He exudes a kind of attitude where he feels that HE is the best. He hurts people's feelings and embarrasses them by revealing their weaknesses in public. And when people ask him to change, he becomes very egoistic and will not accept whatever they're saying.
She wears hijab that covers way past her chest. She reads the Quran a lot and read a lot of hadith. She too, has a lot of knowledge and likes to spread it by giving talks. She takes a lot of pictures of herself to post on social networks because she loves to be praised. She wears dresses up to attract people's attention. She LOVES to be the centre of attention and LOVES it when guys look at her. She has a boyfriend and loves spending her free time watching Korean videos and dramas.
He never misses his prayers, and reads the Quran about once a week. He goes to the masjid when he can to pray as a jemaah and listens to the ceramah. He is nice to his friends and is liked by most. He spends most of his time watching TV and playing games. He does not know as much as Person A and B but he is not ignorant.
She does not wear hijab. She does not miss her prayers. She likes to help at the orphanage and does A LOT of charity work. She gives a lot of sadaqah in secret. She is respectful towards her parents and loves to help around the house. She rarely reads the Quran. She enjoys going to talks. She hangs out a lot with guys and girls and frequently goes out at night.
So which person in your opinion is the worst? Which person sins the most?
The truth is that, they are all the same. They all commit sins. Maybe in our eyes, it looks as if one of them sins more than the others, but actually, they just sin differently.
Sometimes, the good deeds they do are not apparent in our eyes, and it makes us view them negatively. Sometimes, the sins they do are not apparent in our eyes, making us look at them as a positive figure.
And the most important thing is that we do not know what lies in their hearts. It is between them and Allah and we definitely do not have the right to judge. We do not have the right to say that a certain person does not have iman. We do not have the right to call others as sinners when we too commit a lot of sins. It's just that maybe, we commit sins different from them we think negatively of.
So don't be too quick to judge. Yes we can give reminders to people (but remember that we must act upon the reminder we give), but do not simply spread to our friends that this certain person is a bad person. And we must remind our hearts not to think bad about others because well, we are no better than them.
Everyone commits a sin, everyone forgets. Don't judge, but remind each other.