The claim is that random materials contain animal products, including medicines and construction materials, so it's 1) impossible to be vegan 2) hypocritical to claim that carnism is morally inferior to veganism.
This is ultimately an argument that one should not eliminate 99% of the animal cruelty in their lives by ordering something else off the menu because they cannot get the last 1% by changing their entire lives from top to bottom. In no other context is the argument that "one should not move an inch to almost entirely solve a problem because you need to move a mile to completely fix it" a cogent argument.
For instance, some number of humans die each year in car accidents caused by semi-trucks. Does that mean that murder is now justified because "you still kill people just by ordering stuff off of Amazon"? Of course not.
There's no will to remove animal products from things like vaccines or other minor obscure products so long as they are used for food. So saying that one shouldn't be against eating animals because they are hidden in other products is a circular argument because they are hidden in those products only because people eat animals.
Just because someone else does something unethical does not justify your unethical action. Pointing to vegans as hypocritical for engaging in some behavior doesn't actually demonstrate a coherent argument against veganism.
If you're against some product X, don't use it - and simply because a vegan does so in a fashion that you believe is hypocritical doesn't justify you eating animals.