Again, just so we're clear, I don't want Bonds in. But when he takes steroids to improve himself, at least that helps his team. If you are going to cheat, do it in a way that helps your team. Having a guy hitting baseballs like it's a video game helps the team. I don't think what Rose did as manager helped his team in any way.
As to the second question, gambling is a 100+ year problem in the sport. Steroid use has been around for only about 30-40 years and was a widespread problem for only about 20 years. Gambling was never condoned by MLB, whereas steroid use was, at best, ignored until 2003-2004. It would be mighty hypocritical of baseball to sock a lifetime ban on guys they looked the other way on during their playing careers.
But I wouldn't be bothered if proven steroid cheats were banned for life.
If Pete Rose wants his lifetime ban removed, he could start by going on speaking tours talking about the evils of gambling. But it seems his position, then and now, has always been that gambling is no big deal. Ask Michael Franzese what a big deal gambling is.