Seems this site is rapidly becoming a smaller mainstream political site as progressive voices are leaving and being replaced by mainstream Liberals -- and even now a gun advocate.
I don't have a problem with engagement but this is being swamped.
Why not open a forum under current events uniquely for Leftist/Progressive/Socialist perspectives - or whatever you want to call it - views on politics. Then the Canadian political forum can be as advertised (Harper Harpies to...) and people who want to engage with the Liberal party can go there for that purpose.
It could have a sticky perhaps of what the participants could agree on as a condition of being there. So we have a place (when there are so few on the internet) where people who want a more progressive vision than the Liberal party can gather and discuss without a constant stream of Liberal politics and talking points. The Liberals can stay on babble and be challenged in the Canadian politics forum by those up for it while the people who don't want to debate how great the Liberal vision is don't need to wade through that for every comment.
If you don't have a place for progressives who are to the left of the Liberal party to go, they will simply stop coming (already happening).
It is possible that some people would only go to the Leftist politics forum and maybe the Liberals would end up talking to themselves in the politics forum but I am guessing that there would be some who would engage the Liberals in the politics forum as well while others will choose not to and prefer to just stay in the leftist forum. This is better than what is happening now where the people who do not want to engage at every turn with the Trudeau vision are just not coming back.
Moderators would be asking (I hope) for non-leftist entrtists to enjoy the existing Politics forum for wide open debate and leave the leftist space alone. In some respects the model would be like the feminist forum that expects not to argue certain points that are taken as a given so that the conversations can go further than they could if you have to go over the basics in every thread.
Otherwise I don't see this place lasting very long.