Arminian is not by default the anti-Reformed stance - it carries it's own theology which is, to a large extent, aligned with Calvinism (after all, it was derived from Calvinism). There are plenty of non-Cals who are distinctively non-Arminian.
Lutheran is a good example. They reject Calvinism - but their doctrine also stands in opposition to Arminianism. In my area, there are plenty derived from Anabaptist doctrine, which is also non-Arminian to the core but remains anti-Reformed as well.
All Reformed are calvinists
Not all calvinists are strictly Reformed
problem is that within cal/arm/non call are distinct subdivisions that tend to get overlooked/lumped together