Having been a former Catholic some of the rules of what I called "Protestantism" (at the time) were just as "bad" as the Catholic restrictions. I was literally shocked (yes shocked) by the claim that wine was evil, tobacco, dancing, card playing, movie going, on and on, etc...
However I had chosen strict fundamentalism to associate with and simply came to the conclusion that it was what is called (rightly or wrongly) "legalism".
Legalism to me meant going back to an observance of "Torah" as a system of pleasing God. I knew it was wrong because they/we picked and chose of the 613 legal requirements of the Law to keep but simply ignored other "abominations" such as dietary restrictions, mixed fabric wearing, mikvahs for women, etc... Our first church did not even approve of Christmas celebration and if you owned a TV you were suspect. My present day beard would have disqualified me for membership. This one really surprised me as Jesus, Paul, etc are always considered bearded.
But my wife and I "bit the bullet" because of the love of the brethren. We were loud and aggressive fundamentalists of the caliber of JoJ's Grandad, Perry Rockwood, Rolland Starr and many others. I preached in the Boston Common and went door to door in the Boston neighborhoods. Above all we loved the Conventions where one could have one's hearing damaged by the preaching!
We remained that way until long after my graduation from Bible School (which required me to sign a very strict covenant with them).
I know this will displease some but (to shorten a long story) my gravitating away (some would call it an apostasy) from this caliber of "fundamentalism" occurred after an emotional experience in which 1 Corinthians 13 played a large roll in my life and especially
1 Corinthians 13:2 And though I have the gift of prophecy, and understand all mysteries and all knowledge, and though I have all faith, so that I could remove mountains, but have not love, I am nothing.
1 Corinthians 13:11 When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
In terms of doctrine, I am no less a fundamentalist as when I was at our first church (well actually our second) and I still dearly love these brethren. Whenever we visit these brethren we make sure not to offend (suit, shirt, tie for me, dress for my wife) except for my beard - one lady of long acquaintance will not even look at me.
HankD