If the answer provides a thorough and detailed explanation that also happens to be tailored and contextual to the question being asked, that's generally okay. If the person answering the question has provided some anecdotal evidence but also other sources of to back the claims up, I would give that more credibility that just an uninformed blanket recommendation.
It can be a blurry line, but in that case that someone is doing such a thing, I would use this approach:
- Figure out if the person is spamming and flag as such.
- Leave a comment encouraging the user to provide more information in the answer
** Mods can also leave post notices in these cases.
- Mods can also leave post notices in these cases.
- If you are unsure, then you can always flag the answer for moderator attention.
I personally tend to not downvote unless the answer is very, very bad (or harmful) or completely wrong, but you can use this at your own discretion.