They actually do quite well on the Media Bias Chart for a largely opinion based publication, similar to Vox or Slate, so if you're interested in a libertarian perspective on something, they're probably a good source to consider.
If you mean it should be taken seriously because it is influential, then yes I suppose it's worth knowing what they are saying (today that's defending child sex trafficking apparently, but that's not new ground for libertarians). Freep, /pol/ and Stormfront are all influential these days, but that doesn't make them respectable either.
[1] https://pando.com/2014/07/24/as-reasons-editor-defends-its-r...
https://reason.com/blog/2014/07/26/did-reason-really-publish...
... both Ames and Reason link to a scan of the entire issue. I am with Reason: it's embarrassing for Reason that they ran pieces by people who would go on to become figureheads in Holocaust denial, but Ames is stretching the truth rather dramatically about the content of the actual issue.
I don't know anything about Reason and apartheid support. It wouldn't surprise me. The National Review has also been accused of supporting apartheid, and they are the house organ of mainstream conservatism.
It has nothing to do with Trump, but it attracts a personality type who is also attracted to Trump like figures.
https://www.washingtonpost.com/news/posteverything/wp/2017/0...
Many of the casual fans discover the philosophy after reading Ayn Rand or something similar. The noisemakers on AM radio often claim to be libertarian.
Is any of this a particularly fruitful criticism of the coherent political philosophies of Libertarianism, Conservatism and Jerkoff Contrarianism†? I agree with you that, for the most part, it isn't. But it's hardly a 'random slur', either.
†That's what I'm deciding to call (with love!) the coherent political philosophy of TNR.