It is truly not clear that what OP is saying is the explanation you gave, so it was valid to question it.
In any case, “the situation is complex!” is not argument. You have to explain why the person’s view is an over simplification. Declaring that an issue is complex is not enough. There are many complex issues where “X is evil” is still a valid view. Example: WW2 and Nazi Germany.
It is truly not clear that what OP is saying is the explanation you gave, so it was valid to question it.
In any case, “the situation is complex!” is not argument. You have to explain why the person’s view is an over simplification. Declaring that an issue is complex is not enough. There are many complex issues where “X is evil” is still a valid view. Example: WW2 and Nazi Germany.