So I had been looking all over for my friend's secret base, but when he told me it was in a tree near the daycare I knew we would have a problem. See, I already have a friend's secret base hidden there. Is there any way to remove that base so I see my friend's or am I stuck with that base or none at all?

Ask your friend if he can change his base to something that looks like your other friend's current base so you can visit your friend's base and your other friend's base. Problem solved. Hope I helped!