The Buddha's contemporaries

I was reading an article about *The Samaññaphala Sutta* and came across this line: *This [sutta] is placed in juxtaposition to the Buddhist view of the teachings of rival philosophical teachers of the time, showing how the Buddha — in contradistinction to the inflexible, party-line approach of his contemporaries — presented his teaching in a way that was pertinent and sensitive to the needs of his listeners.* Who were these "contemporaries" and what were they teaching?