When in doubt: use Neutral.
In your opinion should the negative tag remain or should I replace it with a neutral?
If you have to ask, I assume you're not absolutely sure, so it shouln't be negative.
It's also wise to ask yourself before leaving feedback: "Does my feedback make Bitcointalk a better place? And if it's negative: is it worth destroying someone's account and reputation over this?". Consider using Neutral feedback if neither Positive nor Negative is justified.
The problem here is that it is not a one to one case. If it was that, i would have also suggested for a Neutral. The probelm here is that if you give him Neutral for his semi-favorable wording for the scam site, the others might also jump in and demand for the same treatment.