From time to time, someone I first encountered on a forum (example: genealogy or photography group) wants to friend me on Facebook.
I have to tell them, as gently as possible, "Sorry, I don't do friends. My Facebook is for immediate family and for groups only, and even most of them, I unfollow." I have held my Facebook friends tally to the mid-thirties for several years now.
The problem with having "friends" online is that they may have expectations of you. They may be insulted if they "like" your stuff and you don't "like" theirs. If they DM you, they think you're going to respond. Etc.
I'm not online for any drama and I just don't want to go there.
For yourself, make your own decisions about "friending" but it's entirely acceptable to just decline the friend request in the first place, citing a personal preference.
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A finger in every pie.