"Who are you to judge someone else's servant? To his own master he stands or falls. And he will stand, for the Lord is able to make him stand... Let us therefore make every effort to do what leads to peace and to mutual edification." -- Romans 14:4, 19
Where I grew up there were occasions when neighborhood pranks would take a bad turn. One such prank was the use of Coke poured on someone's car. Over night the chemicals in the soft drink would eat into the paint finish. The soda would taste sweet but have the power to damage.
The process of judging someone with a critical attitude is very much like Coke on a car. It may seem sweet to the taste to talk about others and put them down, but over time this practice will damage. It eats away at relationships as well as the heart of the one who criticizes.
Do you find it easy to find fault with your brother or sister in Jesus? Is it your expectation that they follow the Lord in the same way as you? Remember, we are all the Lord's servants, unique and accountable to him. Rather than pour acid on others, learn to accept them without passing judgment. Build up, don't tear down.