What if someone is not an Arminian but you want to be able to publicly make people believe he is an Arminian without being able to be accused of lying?

You accuse him of being a modified Arminian

What if someone is not a Roman Catholic but you want to be able to publicly make people believe he is a Roman Catholic without being able to be accused of lying?

You accuse him of being a modified Roman Catholic.

In this way, you can smear a fellow minister as an Arminian or a Roman Catholic but, technically, you have only actually said that the man is not an Arminian or a Roman Catholic.

If the language of modification gets too old, then you can alternate with expressions like “borders on” or “comes near to.”