When should someone no longer be allowed to frequent a masjid?

When is it justified to let someone know that they are no longer welcome at our masjids?

Are we to tolerate someone whose beliefs are 100% aligned with the Quran, yet their behavioral conduct is that of an aggressor or tyrant?

For such people God tells the believers that it is their duty to fight the aggressing group.

49:9 If two groups of believers fought with each other, you shall reconcile them. If one group aggresses against the other, you shall fight the aggressing group until they submit to GOD’s command. Once they submit, you shall reconcile the two groups equitably. You shall maintain justice; GOD loves those who are just.

Or should we welcome someone whose behavior is 100% aligned with the Quran, yet their beliefs are openly in defiance to the teachings of the Quran?

For such people, God informs us that as long as they don’t fight us and they mobilize in the cause of God along with us we can still even consider them friends.