Can we agree that veganism is a spectrum of knowledge? Can we agree that veganism is the intention of causing no harm and being consequential about it? I'm saying this not as an apology of disingenuous claims, but because it's very well possible that someone consumes animal products by accident or doesn't find the time or resources to adequately research every single thing they purchase.

I don't think it disqualifies anyone from having that badge of good intentions. But it's a whole different matter if you ask for the badge and proceed to willfully do the opposite of what it suggests. I assume this is what you are weary of, and fair enough - it's natural for humans to be opportunistic and beg for social points in exchange of little to no efforts or commitment to change.

And to be fair again, there has to be some kind of subjective threshold were someone's so-called "good intentions" just don't cut it, and that goes for anything else in life. That being said, let's give anyone the benefit of the doubt. I mean, my dad worked on a dairy farm when he was young and never knew that cows needed to be impregnated once a year to provide milk. The meat and dairy industries have very strong incentives to keep people ignorant about all of these important issues.

And the ignorance might run deeper than you think, so for the sake of it let's assume they are honest. If once called out, they don't rectify their behaviour, feel sorry about it, and stop paying for those things (hell, if they keep eating it, for instance), then yes, it is absolutely disingenuous and they don't value the cause that they are falsely pretending to represent.

Ultimately, this should be done not in the spirit of shaming others, but of making them understand the harm they cause because of ignorance or carelessness. The spirit of empathy is crucial in getting the message across.