I don't know if I agree. Whatever the platform says, the GOP have been active climate change denialists for decades (unless my memory is way off). They supported torture, the invasion of Iraq (along with many centrist Dems), the propaganda that Iraq was going well, and much more. They impeached a President for political reasons. They've been using dog-whistle politics to appeal to racists and their agenda since the 1960s (look up the Southern Strategy, or for a succinct explanation find the famous Lee Atwater interview).
Maybe it's a matter of degree (well, of course it is), but I don't think the degree of change in 2008 is that great. George W Bush, Dick Cheney, Don Rumsfeld, and the rest were considered pretty radical.
"Are you going to the gym? Did you sneak a cigarette in on Friday night? Did you have a chili dog or a salad for lunch)? Oh you won't tell us? Don't worry you don't have to. Okay we'll just slap a surcharge on your health insurance!"
What's also interesting is that in other western democracies, it's the left wing that's heavily fractured and damaged by infighting, with the right-wing generally able to get along and not get sidetracked by ideological purity. In the US, it seems to be the other way around.
Just compare the 2008 Republican Party platform [1] to where they stand today. A couple things that illustrate just how different the 2008 GOP was compared to today.
On climate change:
> Because Republicans believe that solutions to the risk of global climate change will be found in the ingenuity of the American people, we propose a Climate Prize for scientists who solve the challenges of climate change. Honoraria of many millions of dollars would be a small price for technological developments that eliminate our need for gas-powered cars or abate atmospheric carbon.
There are several other mentions of climate change in the 2008 platform. To the extent that dealing with climate change and economic growth are at odds, they wanted a balance close to growth than Democrats did (and do), but they knew that climate change did have to be dealt with.
On renewable energy:
> Alternate power sources must enter the mainstream. The technology behind solar energy has improved significantly in recent years, and the commercial development of wind power promises major benefits both in costs and in environmental protection. Republicans support these and other alternative energy sources, including geothermal and hydropower, and anticipate technological developments that will increase their economic viability. We therefore advocate a long-term energy tax credit equally applicable to all renewable power sources.
If you want to get banned from /r/republican, just wait until the next time cap and trade comes up, and someone says that it is a socialist liberal democrat commie approach, and point out that Ronald Reagan used it for the phaseout of leaded gasoline, and the first Bush used it for reducing the emissions responsible for acid rain, with overwhelming support from Republicans in Congress...and you will likely get banned from that subreddit for advocating anti-republican positions. Yup...RONALD REAGAN is anti-republican in today's GOP. (Well, his policies are...they never miss a chance to praise him or claim to be like him).
[1] http://www.presidency.ucsb.edu/ws/?pid=78545