Looking for 2 words or phrases to describe this situation

The pastor might be characterised as pertinacious or (persisting):

Continuing stubbornly or tenaciously despite challenges; Holding firmly to an opinion or a course of action (WordHippo)

As for the students, I would say:

The students then looked at each other unconvinced.

M-W defines unconvinced as:

not brought to believe or accept something by argument, not convinced

• They remain unconvinced by her new evidence …

The pastor is sophistic and the students are sceptical.

Sophistic pertains to

sophistry = subtly deceptive reasoning or argumentation

Merriam Webster

Sceptical = doubting that something is true or useful:

Cambridge Dictionary

I also suggest that the students were leery of his arguments:

Leery = SUSPICIOUS, WARY —often used with of leery of strangers

”She seemed a little leery of the proposal.”

Merriam Webster

Note that "leery of" may suggest the verb "to leer" but this is entirely inappropriate and should not be used in this context. One can be "leery of" an argument or an idea but the students themselves do not leer.

to leer = to look at someone in a sexually interested way

Cambridge Dictionary

The students may have looked dubiously at each other.

dubiously = in a way that shows you feel doubt or do not feel sure that something is right or true

Cambridge Dictionary