I have a couple of questions for you knowledgeable webmasters.
1. If I owned a forum that got overrun with spam, ignored it for 2 years to the point it had 1,000,000+ posts. I then delete the DB and redirect to my main site. At this point I notice that the site has a lot of pharma backlinks from 1000's or domains (now all point to my main site).
2. I purchase a website rather cheap and soon find out that it is linked to by an Alexa 100,000 website. This site has placed a link on over 100,000 pages (the home page) - The purchased site is pointed to my main site.
1. As it has all these bad links, I would not risk redirecting that forum to a main site. What is the reason for the redirect? Does the forum get lots of traffic you wish to keep?
2. I am affraid this shows it is good to do site analysis before purchasing the website. Are these links bad? What was the reason for purchasing it? Type in traffic, or the site traffic? You can try to disavow these links and then send the reconsideration request to Google explaining you are a new owner in a hope they will "reset" the domain history.