Avoiding Roundup Ready seeds because of "harmful herbicide" (presumably glyphosate) is like avoiding using microwaves for cooking. Sure, there is some minute amount of risk involved, but it's hard to believe that someone who avoids either is actually making an informed choice.
There is no comparison between glyphosate and "microwaves for cooking". The World Health Organisation believes glyphosate is probably carcinogenic to humans[1] and the EU is still wavering on banning it. It's (very) far from conclusive, as the report states, but to suggest that people only avoid glyphosate due to ignorance is simply not true. There are warnings which warrant more research and it's perfectly understandable why people are uncomfortable.
I'd encourage you to read this[1] article as it seems you are confused about what the phrase "probably carcinogenic" means in the context of the IARC report. In particular, the report does not assess risk which is what you care about when making a (rational) choice to avoid/not avoid particular substances in your diet. Interestingly, the WHO does report on risk and in their evaluation they found "glyphosate unlikely to pose a carcinogenic risk to humans from exposure
through the diet"[2].
