It does seem a little unreasonable to post this on social media, as it is really not that big a deal. However being a 'local' in CO I can also understand that it can be a bit frustrating, particularly when you encounter groups. While the roads are often super scenic, steep and winding, some locals are commuting, or just trying to get from A to B and are very familiar with the roads. On mountain road passing can be difficult to do safely, so it is safer for everyone to pull over when you can. With the current surge in RVs in the state, I have been guilty of getting a little frustrated getting stuck behind packs of them and their 'toads' who are (understandably) driving cautiously, but also not being particularly courteous to other drivers be pulling over when they can.
Unfortunately this may also be coloured by some animosity towards Texans in Southern CO. While I am sure as WtW folks you all were not part of the problem, but there has been some tension between locals and tourists, particularly with regard to ATV and Side by Sides (not so affectionately known as 'Texas Golf Carts') in some of the mountain towns. Many of these tourists are 'proudly' from Texas (you know the type), which may have lead to some unfair stereotypes.