There is negativity from airline guys who always think the grass is greener, but this is just the nature of this job and its something you have to deal with.
There is also just as much negativity at the bottom level with instructors who didn't make it and still have a chip on their shoulder which transfers to their students. I would say that is much more common.
Either which way your always going to run into negativity, either on here or in the air, this job is full of resentment. Either from older guys who don't like young guys flying jets when they was at the same age they can remember what they was doing, or guys who never made it all who of course will have bitterness and advise you its impossible.
Its up to you to remain focused and try and blank it out if your really keen about the job.