[22b top] Beis Shammai’s student: Beis Shammai prohibited items (that would be allowed once they were purified), but permitted items that would otherwise not able to have been cleansed. This was done because is they just prohibited everything (even the ones which would have been able to have been ruled lenient by), the lesser practicing Jews would not have followed either law (because they would incur too great a financial loss) and this would cause more nonobservance in the community.
E’s Lesson: To rule something as prohibited is generally easy, but it takes coming up with deep thought and some clever Halachically permissible rulings to make things permissive. We should never be too strict with people, especially when they are trying to become more observant. We must always care for our fellow and help them along a path back to Hashem, if we can find permissible easier ways for it to happen.