A proper understanding of the Law was meant to give people the key that would help them enter the Kingdom.
But the Pharisees, by twisting the Law so as to use it to justify their own murder, harshness, hypocrisy, extortion and sexual immorality, hindered people from acquiring the true understanding of the Law which might otherwise have prepared their hearts to enter the Kingdom.
The Law was meant to explain Kingdom-qualifying qualities such as love, mercy, patience, morality, justice, godliness and holiness.
But the Pharisees' misinterpretation of the Law robbed people of the benefit that a proper understanding of the Law could have given them, namely it could have explained righteousness and love and brought true heart repentance. But instead, the Pharisees' converts became twice the children of hell as themselves!
Entering the Kingdom required believing on Jesus, and repentance. A true understanding of Law - of God's righteousness and love - could have been the key that might have inspired that belief and repentance. But the Pharisees robbed people of the correct understanding which might have otherwise inspired that.
The Pharisees didn't only make the mistake of twisting the Scriptures to justify harshness. They also made the mistake of twisting the Scriptures to justify sexual immorality and other wrongs. Both mistakes could produce a lifestyle in our hearers that could hinder them from entering the Kingdom, in which case we would be responsible.