Not his best idea, no, but he was giving Moro a chance, just as he did with Frieza on Namek. He doesn't like to kill if he can help it, so he was giving him a chance. He knew for a fact that he could beat Moro even at full power, which was why he gave him the bean. He didn't realize though that Moro had copied Merus' power, or that he could merge with the planet. Based on the info he had though, Goku had this in the bag no matter what happened. he was just... lacking certain information.
AARRRGHGDHDHFIFOSKEKRKTT never give that man senzu beans
Not his best idea, no, but he was giving Moro a chance, just as he did with Frieza on Namek. He doesn't like to kill if he can help it, so he was giving him a chance. He knew for a fact that he could beat Moro even at full power, which was why he gave him the bean. He didn't realize though that Moro had copied Merus' power, or that he could merge with the planet. Based on the info he had though, Goku had this in the bag no matter what happened. he was just... lacking certain information.