They aren't anti-heroes.
An antihero or antiheroine is a leading character in a story who, unlike a traditional hero, acts in an unheroic manner and lacks conventional heroic qualities such as idealism, courage and morality.
Being an antihero is just being a hero who isn't afraid to get their hands dirty, but they still have a moral compass in that they try their best not to do anything that is unnecessary.
Obito used Kurama to attack Konoha out of spite, that had nothing to do with the Moon's Eye plan. Nagato thought that bringing pain to every individual would create peace...peace out of fear. Things like this completely pass moral boundaries, especially considering there were alternatives to their choices on how to bring peace. Much of what they did was out of anger, not to help (though, helping to bring peace was the core goal).
Nagato and Obito are anti-villains at best. They can also be well-intentioned extremists.