It isn't like Arians sought out the media to make this comment. I am sure it was posed to him like it was to Fisher about how tough the NFC West top dogs look. And just like Fisher, Arians gave the response I would expect every NFL coach to make. NFC West divisional fans may see the dominance, he hasn't been religiously following them and to him, he doesn't see the dominance.
I don't understand what fans of the Seahawks want him to say. He isn't and shouldn't be trying to tread lightly. His owner (or was it the new GM) stated the 58-0 loss was an embarrassment that the organization never wanted to forget and live through again. Arians was hired to make sure that type of effort never happens on his watch. He cannot do anything but take the question head on and provide a bravado. Otherwise, his market eats him alive.
I am sorry, but if I am setup with one of those kiss the rings questions from local or national media while I am trying to turn around my team, I am not going to fall in line with the national story of how great the top dogs are.
It isn't like Arians was pulling a Rex Ryan and taking swipes at the Patriots from day one of his run as the Jets coach. No on in the NFC West has attained the same level of dominance that the Patriots had when Ryan came along. 9ers had a great 13-3 run, but missed the Superbowl. They followed it up with a Superbowl appearance. That is why Arians states one of the two has a chance of being dominant. To take his comment further, he sees a team that went 7-9, 7-9 and then caught fire to go 11-5. Another that was 6-10, 13-3 and 11-5-1.
Personally, I see dominant as a long term thing record-wise and play-wise. Maybe the reporter was thinking physical dominance and Arians was thinking long-term performance (physical and record) dominance?
Anyway, it is something to get fired up for but the proof will happen on the field. The rest is just good material for football discussion boards.