The Nationalist supports the wineries in the country or territory resided in. The support may be even narrower than that and be limited to provinces/states within a country. For example a Canadian residing in the province of Ontario could decide to drink wines from all provinces of Canada or may focus on wines from Ontario. An American in New York could decide to support wines from New York. The Nationalist support could be an absolute or a preferential one.
The Nationalist supports not only the winery but all facets of the economy involved in wine production that would include but not be limited to labour, transportation, winery equipment and supportive professional services. It is not simply a bottle of wine but the spin-off benefits of wine production to the economy.
Commendable as if your local economy benefits well then so do you.
If your chosen jurisdiction makes a wide variety of wines the Nationalist approach just might satisfy the palate but that is a rare jurisdiction. For example in the province of Ontario if you prefer red wines you can cruise along with Gamay, Marechal Foch, Cabernet Franc and perhaps Pinot Noir but no such luck can be found with so many other grapes not even grown in Ontario such as Carménère from Chile . A Nationalist wine drinker might fare even better by focusing on wines produced throughout Canada which would include British Columbia, Quebec and Nova Scotia but still so many wines are produced ex-Canada the Nationalist would be depriving themselves out of a vast array of wines. Some wine drinkers can co-exist with that deprivation. Some can’t.
On occasion politics may come into play. When the Trumpster was on his blustering mumbles insulting Canadians (and just about everything else but himself) I encountered many Canadian wine drinkers happy to give a cold shoulder to American wines.
There is no need to criticize the Nationalists as if they are a happy lot why butt in! You may love that foot trodden Touriga Nacional from the Douro but the Nationalist couldn’t give a damn.