...So what's the reasoning that seed oils are bad? Scientific backing? Seems to be a trend that it's unhealthy or whatever
Im not giving up peanuts anyways 
High omega-6 content, I assume
They are precursors of pro-inflammatory mediators, whereas Omega-3 fatty acids act as polar opposites - they inhhibit inflammation.
Since both types bind to the same enzymes when they go through their respective metabolism (various elongases and desaturases), it leads de facto to a substrate competition problem.
You need both, but it's easy to see why an omega-6 to omega-3 ratio that is too high isn't great, health-wise, in the long term.
