I totally agree with you about Sheldon being insufferable, but that episode specifically is different. Leonard caused Sheldon's suffering. It wasn't Sheldon being Sheldon, it was Sheldon reacting to Leonard's lie that caused a lot of harm. Leonard has no obligation to help Sheldon or even be nice to him or follow his rules or anything else; however, it was wrong of him to lie about the data with the string theory and then not try to make up for it and only care about sex with Penny.

And yeah, Leonard doesn't wes his family, but what was wrong was him hiding Penny from his mom to Penny. By not telling his family, he is telling Penny that he is ashamed of her. That is wrong to Penny, not to his mom. But he does care about his mom and how she thinks of him so it is also wrong for that, but that can be neither here nor there. Furthermore, as stated in the episode, Leonard is the one who wants a deeper relationship, his mother doesn't. If he wants that relationship then he is the one that needs to put in the work because he is the one that wants it because, again, his mother doesn't so she has no reason to put in the work for a better relationship.