on the other hand using bitcoin doesn't have that fee. so if they get paid in bitcoin they can offer their goods at a "discount" and that can create incentive for people to make payment in bitcoin hence increasing adoption.
This is undoubtedly a very interesting way of looking at this situation. For the adoption of Bitcoin, it would be much better if it were seen as a cheaper alternative.
A credit card, for a merchant, does not just have only the cost of that Fee. Usually, it takes a long time for him to receive the money. It can be 10 days up to 30 days. So, it would make more sense for some merchant to start making a discount available to Bitcoin users.