All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, know that the consent of the father is not a condition for the validity of the marriage of his son. But it is more appropriate and more suitable that your colleague does his best to please his father by convincing him of this marriage and clarifying to him the harmful effects of delaying it for a longer time. In fact, any delay can drive this colleague to temptations which may result in committing what is forbidden.
Moreover, if his father's refusal is not due to a legal reason, then it is but obstinacy. This will cause his son to lose an advantage and, in this case, his father commits a sin.
Anyway, we prefer that your colleague does not get married without the consent of his father and the other members of his family. If his father insists on his stand, it is better to fulfill his father's desire although this is not obligatory. But pleasing one's father is pleasing Allah. No doubt that if Allah is pleased with someone, He will grant him means that he never expected.
Allah knows best.