Its a choice, would you rather have less Jews but who are more committed or more jews some of whom are less committed.
We can discuss these things in the abscract what you think is better. But the reality is in life you will likely come into contact with such people and you will need to make decisions based on that.
If your Kid tells you he wants to listen to Rock Music and have a BF/GF but will keep Shabbos and Kosher will you disown him or give them mussar and perhaps drive them away or would you still love them and let them make those choices and be happy they are shomer shabbos.