A great many landowners are not.
B) Glyphosate resistance doesn't affect a plant's resistance to non-glyphosate based herbicides.
All of which are more toxic and usually more expensive.
If the neighbor isn't using a glyphosate herbicide, he shouldn't care if a weed has glyphosate resistance.
"Shouldn't" according to whom? What do you know of what I do? I am absolutely dependent upon glyphosate.
I have a neighbor who has a 50 acre vineyard. He lets every single weed blow seed a lot of which ends up on my extremely steep (much of it nearly vertical) and erosive native plant reserve. I have 317 plant species, of which 97 are weeds. My goal is to develop the means to separate the two. My property may be the cleanest piece of land on the entire Central Coast of California. If those weeds became glyphosate resistant, I'd be hosed.
I employ probably 20 different control processes, many of which are cutting edge technology, probably a third of which rely upon glyphosate. Because I have such steep land, there are several riparian corridors hereon. We have restrictions on what I can use there. Glyphosate is an absolutely indispensible tool in such places. Rendering the weeds glyphosate resistant would be a disaster for me. Giving Monsanto a pass for causing that loss isn't just.
If he is using a glyphosate herbicide, he doesn't have much of a complaint against his neighbor.
I do habitat restoration research and development. I operate in the wild. If I had to go hire a PCA and subject myself to inspections by idiot bureaucrats for what I do to do this kind of work, they'd refuse. It's too dangerous. We are too remote. The timing is too critical and you don't know what you are talking about.
In one breath you claim you're dependent upon glyphosate herbicides, but in the next, you complain about how bad Monsanto is for having developed glyphosate herbicides and in the next breath this all becomes you neighbor's fault because, apparently, he doesn't care about herbicides at all.
If glyphosate is truly "indespensible" in your operation, it may be your practice, not your neighbor's, that fosters the propagation of resistant weeds. Roundup is recommended for use on cropland only once each second year.
OK, I now understand more about your operation.
Here is what I would recommend. BTW, I'm a farmer, licensed applicator, etc.
First, get your license. Many of the products that will work are restricted, not because they are "more toxic" -- they're not. It is because many products are controlled (esp. in California) because there are record keeping requirements or riperian issues.
If you don't have an applicator's license, you are shutting yourself off from a great deal of options that will work, are cost effective and are new technology. This is especially true in California. I have a brother who owns land in CA and products I can buy/apply without invoking my permit here in Nevada are under licensed control in CA. Why? Well, all the doggone hippy environmentalists wanted it that way in California.
As I've told many, many people who are now small-acreage landowners: if you don't get your applicator's permit, you're not a serious steward of the land. You're merely a wanna-be. The only products that aren't restricted are either so safe that even an idiot homeowner can apply them without killing everything within a quarter mile, or are "generally accepted as safe", like sulphur dust.
Second: Go get a "Greenbook."
http://www.greenbook.net/
No one who is a farmer/applicator is without one of these.
Third: modern herbicides (ie herbicides labeled after the mid-90's or so) are not "more toxic" than glyphosate. The EPA no longer labels broad-spectrum products. To gain a license now, a manufacture/registrant must deal with the "risk cup" model, which requires greater crop/site specificity, lower toxicity and higher safety margins for animals/fish/humans.
I have a greenbook from 2005 (I don't buy a new one every year -- they're over $200 a copy), but you can find lots of IPM info online.
If you have specific questions, I'd be happy to help as far as I am able.