It reminds me of an international missions conference I went to in Urbana.
Here's a big (10, maybe 13 thousand people) conference (mostly evangelical Protestants) held every three years on a college campus during winter break. It's a wonderful time of prayer and fellowship, and a great recruiting ground for Christs warriors while they are still deciding what to do with their lives.
The odd thing was... every morning before the sun came up, as we trudged through the snow for our 10min walk to the dome... there was this guy standing there trying to evangelize every one of us!
His literature stated very clearly that unless you were baptised into their church, you were damned to Hell. Catholic, Protestant, Evangelical Bible-Believing Charismatic Pentacostal whatever Church - didn't matter. They were all wrong.
He was dedicated though. It was quite cold, but he was there every morning and every evening for the entire week.
The comparison of Fundamentalism to Gnosticism "works" on a number of levels.
1) It establishes that the speaker is an expert on both Fundamentalism and obscure things like Gnosticism
2) It compares the enemy (Protestantism) to a group all acknowledge as heretics (even Fundamentalists, hmmm)
3) It points out the role of the doctrine of the Catholic church and its infinite superiority as it beat back the gnostics once and will do it again