Linebackers are rarely bigger than defensive ends because they tend to try to avoid taking on blockers, generally don't have to worry about getting double teammed, etc. If you believe that weight/size isn't more important at DE, then I can't help you.
I don't think anyone is saying Parsons or Abdul Carter shouldn't play DE. They are top-notch pass rushers, so they should be used that way. The difference between you and I seems to be that I don't believe that either should be used exclusively at DE because offensive coordinators are going to run at them to try to take their legs out from under them.
I love it when other fans resort to the "you just don't understand football" argument. It's such a cheap out in a football discussion. If you believe that weakside linebacker and defensive end have the exact same job description because they both play outside, I'm not sure what to think of your football acumen.