Written by Yoel Lax
It says in this weeks sedra:כשלחו כלה גרש יגרש אתכם מזה - When he sends forth it shall be complete - he shall drive you out of here - יא:א
Q) Why didn't Pharoah let them leave, why did Hashem have to make him force us out?
A) The Heiliger Sfas Emes (who is my great great great great uncle and it is his yahrzeit this shabbos!) says that Hashem didnt want to liberate them just from exile, but from every vestige of Egyptian Influence. By having Pharoah Drive them out, he ensured than any connection between Klal Yisrael and the Egyptians would be severed. This would allow the Jews to be spiritually unencumbered and so they would be able to reach the spiritual heights necessary for receiving the torah and entering the land of Israel. Had Pharoah freed them willingly, they would have remained morally debted to him and spiritually tied to Egypt, unable to be truly free.
R' Yitzchok Zelig of Solokov embellishes on this approach: Whenever one shows kindness to another, it creates mutual affection and forges a connection. The Jews would of felt gratitude to the Pharoah if he let them leave, thinking he had changed his mind and liked them, and maybe they would, chas veshalom go back later! Hashem therefore had them chucked out so they would not return!
(PS: the Torah does say 'For if you will take an egyptian' or something like that, as even though we were oppressed in their land, we still have to be grateful for them giving us 'accomodation' for such a long time, and thats why we only say half hallel on pesach as we are upset they had to die)