否定 and 反対: denying content and opposing a plan
Compare denying a rumor’s content with explaining opposition to a plan. Distinguish the spatial meaning of 反対側 and keep denial separate from verification.
Denying content or rejecting a value
否定 (ひてい) means denial or negation. 「本人はうわさの内容をきっぱり否定した。」 says the person concerned firmly denied the rumor’s content.
「失敗したからといって努力まで否定する必要はない。」 says failure does not require rejecting the effort as well. Failure and the value of the effort are not the same judgment.
Opposition to a plan and an opposite side
反対 (はんたい) can indicate opposition or the opposite side. 「私はその計画に反対する理由を説明した。」 describes explaining reasons for opposing the plan.
「郵便局は駅の反対側にある。」 locates the post office on the opposite side of the station. 反対側 here describes a location, not an objection to the station or post office.
Judging content and judging a course of action
Denying the rumor concerns not accepting its content; opposing the plan concerns not supporting that course of action. A statement can both deny a claim and oppose a plan.
The person’s denial does not establish that the rumor was verified as false. Read who denies which content separately from who opposes which proposal.
What is denied in 「本人はうわさの内容をきっぱり否定した。」?
Show the answer and why
The rumor’s content. The sentence states the person’s firm denial, not opposition to a plan or an objective verification of the rumor’s truth.

