This answer should not have been marked as offensive.
Mentioning suicide bombers is not offensive in itself (if it was, a lot of news reporters would necessarily be offensive). These people do exist in the world today, and nobody should be penalised for mentioning their existence. Nor should someone be penalised for guessing that this may be the answer to a riddle, when it does seem to fit most of the clues. If some new user posted some troll answer about suicide bombers, then by all means delete it - but what happened here was an experienced and respected user making a serious attempt at answering a riddle and being penalised for it. (Literally penalised: a post marked as offensive loses the poster 100 rep.)
We should be allowed to mention political subjects, as long as we do so in a polite and respectful manner. Abuse and hate speech is not acceptable anywhere on Stack Exchange, but if any mention of politics on PSE deserves to get marked as offensive, then there should be a statement in the help centre to this effect and consensus on meta to determine this policy. Frankly I might stop using the site if this becomes policy - if someone writes a riddle about Adolf Hitler or Donald Trump, I don't want to risk being marked as offensive for posting the correct answer.
From the canonical main meta post about offensive flags:
Even if a post is a bad post for some reason or another, it is probably not rude or abusive. The rude or abusive flag (formerly known as offensive) is meant to be used only in extreme cases, like hate speech, abuse against people, or abuse of the community or system.
As a rule of thumb, if you can’t justify something being hate speech or abuse, you shouldn’t mark the post as rude or abusive. Instead, you should downvote the post.
If an otherwise valid post contains vulgar words as an expression of frustration, edit the bad part out instead of flagging the entire post as rude or abusive.
The answer under consideration here clearly does not qualify as "hate speech or abuse", and thus marking it as offensive was against SE policy. If you think it's not the correct answer to the question, downvote it; if you have >20k rep and you really think it's not worth keeping around, vote to delete it; but this answer is not rude or abusive and should not have been flagged as such. If you object to the specific choice of phrasing "human bomb", then edit the post to change it to something more accepted such as "suicide bomber". (I would have done so myself right now if the post wasn't locked due to having been marked as offensive.)
The correct course of action now is for a moderator to clear the offensive flags against it, thus unlocking and undeleting the post and restoring the lost 100 rep to the answerer. They, the OP, or anyone else can then edit the post if desired. I would like to request that one of our moderators do this, in the interests of fairness to the unfortunate @AeJey :-)