لَا تُكْثِرَنَّ الضَّحِكَ فَتَذْهَبَ هَيْبَتُكَ وَلَا الْمِزَاحَ فَيُسْتَخَفَّ بِكَ
Do not overdo laughing as it will diminish your esteem, and do not overdo joking as it will diminish your worth
مِنَ الحِكمَةِ طاعَتُكَ لِمَن فَوقَكَ وإِجلالُك مَن فِي طَبَقَتِكَ وَ إِنصَافُكَ مَن دَونَكَ
It is wise to obey those who are above you, respect those who are in your rank, and be fair to those who are below you.
ثلاث لا يستحيى منهن: خدمة الرجل ضيفه وقيامه عن مجلسه لأبيه ومعلمه و طلب الحق وإن قل
Three acts are not considered demeaning: serving your guest, vacating your seat to your father or your teacher, and demanding your rights no matter how small they might be.
In social gatherings in ancient Arabia (and maybe still to this day), your position or seat in the gathering depends on your social status. Leaving your seat to someone who just joined the gathering is considered a respectful act.
The Imam is telling us that these three acts are not shameful or degrading. Being polite and kind to others and demanding your rights are therefore good habits to have.