we play that if it says destroy a minion the card means other players minions
Then you're playing wrong. There are times where it is beneficial to destroy (or return) your own minions and there are times where you have no choice but to destroy them so unless "other player" is specified your own minions are a viable target.
From the rulebook...
Smash Up Rulebook, page 9 wrote:
You must follow a card's ability, even if it's bad for you. However, if a card says you may do something, you have a choice whether to do it.