Is breaking off an engagement due to the suitor's inability to control himself and his claim of love considered an injustice to him and an ingratitude for God's blessings?

An engagement is merely a promise of marriage, and either party may dissolve it. If the young man is pleasing in his religiosity and character, then it is better to accept him as a husband, for the Prophet, peace and blessings be upon him, said: "If there comes to you one whose religiosity and character you approve, then marry him. If you do not do so, there will be tribulation on earth and widespread corruption." The abundance of those who commit sins does not justify the sin nor does it lessen the punishment. Consult those of sound judgment, seek guidance from Allah, and there is no blame in rejecting the engagement.