Another flavor of “its ok to sin” is that some sins are small and, therefore, harmless.
There is no such thing as a little sin. Even small things form steps on paths to great outcomes:
...out of small things proceedeth that which is great. (D&C 64:33)
You have no way of telling which “little” infraction is actually a critical step away from something of great value to you:
6 Now ye may suppose that this is foolishness in me; but behold I say unto you, that by small and simple things are great things brought to pass; and small means in many instances doth confound the wise.
7 And the Lord God doth work by means to bring about his great and eternal purposes; and by very small means the Lord doth confound the wise and bringeth about the salvation of many souls. (Alma 37)
God weighs so-called little sins quite heavily:
10 He that is faithful in that which is least is faithful also in much: and he that is unjust in the least is unjust also in much.
11 If therefore ye have not been faithful in the unrighteous mammon, who will commit to your trust the true riches?
12 And if ye have not been faithful in that which is another man’s, who shall give you that which is your own?
13 No servant can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon. (Luke 16)
We must always remember that the little things are the big things. Our conscience must be obeyed, even in and especially in the smallest of things.
Your conscience includes accountability for all the little things that no one else knows about. Your conscience will not excuse you for deviating in the least from your true best, even if everyone around you thinks the world of you. Your conscience will not excuse you for deviating from your ideal, even in ways where no one else will ever know.
For example, it is easy to give the impression that you care about other people when others are watching you. Some people say all the right things and participate in charitable giving, but don’t actually care very much about anyone else. As soon as it is inconvenient to help others, they stop. When their conscience prompts them to do something that will cause others to judge them poorly, or when it costs them something they want, they will ignore the needs of others.
This ought not to be so.
If a man say, I love God, and hateth his brother, he is a liar: for he that loveth not his brother whom he hath seen, how can he love God whom he hath not seen? (1 John 4:20)
Your conscience will not give you a pass when you knowingly do less than your best, even in the deepest, most hidden parts of your desires and acts.
There is nothing that is hidden with God.
Woe unto them that seek deep to hide their counsel from the Lord, and their works are in the dark, and they say, Who seeth us? and who knoweth us? (Isaiah 29:15)
Seeking deep to hide your counsel from the Lord is to lie to yourself in the motives for your actions or the actions themselves.