Inprogress:
I think the resentment is somewhat the same as what I have when I look at my salary (when I still worked as one) being an Industrial Engineering Technician who spent a ton of money learning a ton of stuff, only to see the just out of school girl work as a PA at a higher salary. Same kind of resentment which is based on nothing more than being angry at the situation as it was when you went through it. Now anyone can basically learn anything either free or very very cheaply and make a good living out of it without the need of a big university piece of paper.
I think you hit the nail on the head but you really need to expound on it.
It really depends on the motivation of the person with the anti-arduino sentiment because some of them have interests in other microcontroller companies and Arduino is sucking the business from them. A retired professional in the industry recommended the Arduino to me because it is one of the easiest to learn because it comes with a bootloader and bootloaders make things easy because it does things for you.
One of the pros is that it works with the C language. C is the language of engineers for now.
Another pro is that it comes on its own little development board and there are daughterboards (called shields) that work with it.
The criticism is that the Arduino was invented for art students and that you aren't really interested in learning microcontrollers. The truth is that microcontrollers can be hard to learn and that there is a learning curve. In a truth, people are jealous because they spend a lot of time learning and you can go on the web, buy a daughterboard and cut and paste some code and you are on equal part with someone who is learned...Well, almost. The truth is that you have to start somewhere and this is as good a place as any.