That reference uses Exodus 23:2 as a scriptural reference supposedly to back up the thought that just because others do it, ignorant of any possible symbolism, that's no reason for Witnesses to do it.
The verse says:
You must not follow after the crowd to do evil, and you must not pervert justice by giving testimony to go along with the crowd.
Even this verse suggests a link with a legal application. This becomes clear with the context. Here are verses 1-3:
You must not spread* a report that is not true. Do not cooperate with a wicked one by becoming a malicious witness. 2 You must not follow after the crowd to do evil, and you must not pervert justice by giving testimony to go along with the crowd. 3 You must show impartiality in the dispute of a poor person.
This is obviously related to prohibitions on perverting the course of justice by either giving false testimony, being swayed by the crowd to change evidence or not being impartial with evidence regardless of the social and material standing of the accused.
Accepted, there is a principle that says you don't have to do something just to follow the crowd but there is no other scriptural evidence that specifically prohibits or even questions the appropriateness of toasting. If the WTS was consistent in it's application of prohibitions to everything that had some potentially pagan source then perhaps it would be reasonable but they are not. Even the above WT reference uses examples like pomegranates and the raising of hands to illustrate that other things may be construed to have a pagan association yet were acceptable.
Just like things like blood the logic is inconsistent and without foundation. As Anders says... it is wrong because the WTS says so. I don't think I've ever come across a Witness that does it and claims it's a matter of conscience however I may just give it go sometime just for a laugh.