You really do have it backwards, they are not the ones being arrogant.... French province, French signs, most road users read French, when in Rome... I am not fan of the Quebec language laws but in this case they are doing nothing arrogant or wrong, signs match what the locals (and most road users) speak and read. Most of the non-local road users also have no issues here.But it's the TC and there are 3-5 provinces either side that don't speak french, hence the arrogance.
Expecting them to bend to suit a minority of road users passing through that won't or refuse to take the basic effort it takes to understand the signs, that IS arrogant.