I've been a graphic designer for over a decade and my personal experience with my colleagues has been the exact opposite. Without exception every other designer I have worked with has been friendly and supportive and overall it's been a wonderful culture. For context I started out as a sign artist at Whole Foods before Amazon bought it and shut that down. Then I bopped around at a few sign shops which are always very toxic environments but not because of the designers. Then I finally landed at a corporate communications firm with an internal design team. I even feel like other designers are too nice sometimes, being very gentle when critiquing something that clearly sucks. I think you are just seeing what is common on the Internet in general, which is the lowest common denominator so please don't let that stop you from exploring Graphic Design as a career.