A couple of things:

I have verifiable evidence than Marijuana is both addictive and harmful

unless you've conducted double-blinded randomised controlled trials, you don't have evidence, you have anecdotes. Yeah, that sounds kinda dickish, but it's really important.

no one should dictate what plants others can eat

That's pretty ambiguous. First, we're not just talking about eating, we're talking about using in other ways too (in this case, smoking). Second, we already regulate other plants/products, like alcohol and tobacco.

For me, it's pretty simple. Marijuana does not cause sufficient harm as to warrant making it illegal. If an informed consenting adult chooses to smoke, drink or get stoned, that should be their choice. Obviously you shouldn't be drunk or stoned while driving or doing surgery or caring for kids, etc, but we already control for these cases with alcohol.

TBH, as much as I love beer, whiskey and wine, it's much harder to justify keeping alcohol legal than it is to keep marijuana illegal.