In my company, any time we have a goal or a problem that needs to be fixed, we don't really debate and bicker over timelines. We debate over what the issue is, why it's an issue, and what we're going to do to address the issue.
Personally, I don't think there's any way to flip our fossil fuel dependency in the next 12-15 years, but it does seem a tad myopic to focus so much discussion and angst on how long it's going to take. It's a KPI worth setting a goal on but not necessarily one to get lost in. How we get there is the biggest discussion. The fact that a timeline does seem to be such a point of contention among so many conservatives heavily suggests that the timeline isn't really the issue; at least, it's not the real issue.
There's a lot of power and wealth in fossil fuels, and from what I've read, the vast majority of fossil fuels political funding is going into GOP coffers. So there's obviously a financial element to all this that it is mostly slanted in favor of conservatives (which helps explain why the loudest boo birds are conservatives). I've also been seeing some polls in recent years that suggest younger conservatives are generally much more on board with renewable energy discussions... it's the Gen X/Boomer conservatives (where most of the power/wealth is right now in that group) that are holding it back and in some cases even pushing for fossil fuels expansion.