Inter is a great team, losing to them doesn't really mean much and I believe we are going to see Inter win plenty of games, it is not really a shocking result that they lost this, we should be used to this and not be really that much shocked at all. I believe the best thing to do would be just focusing on how to get better results for Arsenal against weaker teams. If Arsenal could get wins against weaker teams, then losing to Inter level teams is not an issue.
It has to be an issue as they need to win against the tougher team too for them to show strong will to be competing for the title. Just winning smaller clubs won't win you the champions league. Winning against weaker teams will make you feel to relaxed and when you face stronger teams, it becomes hard for you to win. Arsenal can win inter Milan when they have their full squad in shape, Arsenal hasn't had a break since as they haven't been in form for some games now therefore that was the cause of the lost against Inter Milan. Unfortunately there's no return leg as if there was, I think arsenal would have payback to inter milan for the lost that they got.