So if you don't trust Monsanto for most things, you will especially not trust it to tell you the truth about the safety of its products nor about the completeness of their tests to ensure said safety.
It's adamant about the safety of its GMO lines and (in the case of Roundup Ready) the pesticide products that are complementary to them.
It's, OTOH, also a big producer of non-GMO seed and actively markets products to the organic food industry.
When it can't do that, it sues farmers that harvest, plan and grow the seed it wants to protect.
This includes Monsanto's crops contaminating other crops like in the Vernon Hugh Bowman case.
It also promoted (at least in France) round up as biodegradable but we eventually found out it didn't, and went to contaminate the drinking water.
Which is a problem, given that glyphosate based products are currently in the process of being banned in Europe.
The answer from Monsanto to that has been ghostwriting reports and pretend they didn't come from them.
I really doubt your statement.
The primary issue with Monsanto specifically would then be that they actively try to prevent farmers from using non-hybrid seeds. Also, one would be surprised how well grains grow without pesticides, if the land is properly cared for. There was a time before pesticides were as widely available, and they did not have the time to weed the whole field by hand ;)
Farmers aren't stupid. Monsanto has no way to prevent them from using non-hybrid seeds. Farmers will plant whichever seeds they expect to deliver the highest ROI.
Grain production before pesticides was far lower. Back then famines were common rather than something that only happened during wartime. Don't ask us to return to the dark ages.