this is a fallacious line of reasoning. you're falling for the spectrum fallacy.

That's not really an argument for veganism. It's a moral accusation masquerading as a premise. It assumes that eating animals necessitates “harming others” in a morally relevant sense, then uses that assumption to characterize everyone who disagrees as someone who approves of exploiting vulnerable beings. That's basically begging the question with a side order of moral condemnation.

I knew this woman that claimed she was vegan. She was interested in aquaponics. Raising fish for food and using the effluent as fertilizer. Not that she would eat the fish. No, because she's vegan! She was happy to sell the fish to somebody who would, though. She was also interested in raising chickens for their eggs as well as meat chickens for slaughter. Not that she eats eggs or chicken, but she has no problem exploiting chickens and selling their eggs and corpses.

Your purity test is wanting, IMO. As you phrased it it seems pulling weeds could become an ethical crisis.

Not every non-vegan is a bad person, sometimes your social and economical context fights against your ethic; in many countries low-quality meat is cheaper than fresh fruit and vegetables; I'm not saying nothing can be done to improve these paradigms, political measures need to be achieved to reduce animal consumption, a single person has limited power.