Redirects are not bad for SEO, but as with so many things only if you put them in place correctly. A bad implementation might cause all kinds of trouble, from loss of PageRank to loss of traffic. Redirecting pages is a must if you make any changes to your URLs.
301 redirects should be used when a page is no longer relevant, useful or has been removed. They are also really valuable for site rebuilds, where URLs are tidied up into the newer, cleaner pages. It is very important to redirect any old URLs that won't be staying the same on a rebuild of your website.
If you redirect from one page to another, the content on the original page will not get indexed. Only the target URL will be crawled and indexed by the search engine.