Complex sentence: In theology he challenged the ecumenical trend that strove to somehow see a uniformity in all religions, not out of an ill will, but from a conviction that dialogue between religions must be based on a "pursuit of truth".
Split into simpler sentences: In theology he challenged the ecumenical trend that strove to somehow see a uniformity in all religions. He acted not out of an ill will, but from a conviction that any fruitful dialogue between religions must be based on a "pursuit of truth".