Luther taught his personal doctrine of "predestination", (or election), which is similar to eternal security - the "once saved always saved" concept. I don't know a thing about the doctrine of "spiritual suicide", except that I believe Luther surely committed it when he left the Truth to follow his personal beliefs and founded his own church.
What? Just because these two beliefs are part of Calvin's 5 points of belief (TULIP), they are "similar" and Luther taught them? Give me a break. What a pathetic argument.
First of all, Luther never taught once saved, always saved (eternal security). He taught the opposite: You can lose your salvation because salvation is, after all, a relationship with God/JC (John 17:3)...as we all know, relationships are never static...we either are moving closer to God or further away each day...and sometimes that's a roller-coaster...and some folks cut off their relationship with God 100%.
Jesus said many are called, but few are chosen...so just because many folks have been called by God, doesn't translate that they are predestined never to fall...or that they were ever in Christ to begin with. Although Luther taught in BONDAGE OF THE WILL that folks don't have the power to receive Christ, they indeed possess the ability to continue to reject Him.