By the very nature of a 51/49 split 49% wouldn't support something. I don't think anything should be criminalized unless at least 2/3rds of people support it. Theoretically the constitution should protect people's rights against democratic support for something that is wrong but the problem is it's "interpreted" by fallible people unable or unwilling to look beyond their personal biases.
I get what you are saying about abortion. I don't think it's right either. I used to be very vocally anti-abortion much like I am about police. I could even go find old rants I posted here about it, but as a Libertarian I accepted I was in the minority on the issue and moved on. I was never ranting about marijuana legalization until it was supported by a majority of people. While I still disagreed I accepted it wasn't the majority opinion. Only once it became the majority opinion and it still wasn't legalized did I get salty about it. When it was the minority opinion we were told "if you don't like it then work to change people's minds on the issue and vote", so we did, and still got ignored by the federal government.