don’t worry no one is going to be offended just because you ask. more like people are going to be offended, because i said it sounds dumb.
basically, they are grammatically correct, but using them in a situation where they do not belong (= talking to your idols) is inappropriate. like, anata is the polite form of you, but it’s supposed to be used when you have ~a deep intimacy~ or something with the person you are talking to. like a wife talking to her husband. if you want to be polite when talking to a japanese person, use their name instead.
aishiteru is —- well it has a lot ~deeper~ meaning than the english ’ love you’. probably because they have ‘suki’ and ‘daisuki’ and those are ok to use when talking to/about your idols. aishiteru is something even your boyfriend would probably never say. unless he’s proposing to you or something.