The Tetra Fluenz flu vaccine, according to UK medical authorities, has some negative effects (flu like symptoms, not just a pain in the arm) on ≥1:10 recipients, https://www.medicines.org.uk/emc/medicine/29112.
The problem with the simplistic "just get vaccinated" approach is when it fails you've nothing to fall back on because you weren't honest to start with.
"Take this and you won't get flu, it's _perfectly_ safe", the child gets sick from the vaccine, then gets flu anyway. So, now I should trust you? That would be irrational.
Vaccines are absolutely right for public health, they may not (in rare cases) be right for specific individuals. As vaccination rate increases (close to full vaccination) the mathematical reasoning based on not becoming personally sick sides with _not_ get vaccinated.
Moreover, vaccination advice from medics does change, infant flu vaccinations has been pushed back recently. Presumably you'd have people ignore that advice and vaccinate anyway because 'not getting vaccinated is always "idiocy"'? In your opinion it seems 'just disgusting whether vaccination is right is idiocy'?
tl;dr people lying that vaccines always work for individuals is bad in the same way as those lying that vaccines don't work.