There is this person that seems to make fun of me for having a religion -- Catholic or not (this person used to be Lutheran), this person believes that people who go to church are all hypocrites. I just try and hold back my tears. How can I let this person know, not to generalize people by the actions of some? Besides, we are, after all, imperfect beings.
When people use words like "all" categorizing people, they are often inaccurate because few attributes can be applied to all people. To emphasize this, ask this person if all atheists are bad people. Then ask if some atheists are bad. Then ask if he can see individuality in one group, why can't he see it in other groups.
The Bible calls people like this "scoffers." It means that they are people who refuse to believe anything. You can't correct such people directly because they automatically refuse to believe anything you say. "He who corrects a scoffer gets shame for himself, and he who rebukes a wicked man only harms himself. Do not correct a scoffer, lest he hate you; rebuke a wise man, and he will love you" (Proverbs 9:7-8). But it also means a scoffer tends to be basically ignorant because their lack of belief means they won't learn. "A scoffer seeks wisdom and does not find it, But knowledge is easy to him who understands" (Proverbs 14:6). Scoffers tend to think their arguments are iron-clad and sophisticated, so they refuse to believe anyone who points out they are illogical. Sometimes the best answer is just not deal with people who won't think. "Cast out the scoffer, and contention will leave; Yes, strife and reproach will cease" (Proverbs 22:10).
Why answer such a person? The reason is not for the scoffer, but for all the other people listening in. Others can see the flawed reasoning if it is pointed out and they will learn. "Strike a scoffer, and the simple will become wary; Rebuke one who has understanding, and he will discern knowledge" (Proverbs 19:25).
In other words, don't think it is your job to change a scoffer's mind.
But also keep in mind that while we are imperfect, it doesn't mean we accept imperfection. A Christian always strives to improve.