I'd say it's not fake, just misguided. The side effects of the mRNA vaccines are well known, including the elevated chance of pericarditis/myocarditis in males under 30 years old. This seems to be linked to high testosterone levels. Like the clotting issue its rare for it to be of significance, otherwise numerous in that age group around the world world be dying of it now. Inflammation of the heart is actually proving more common than thought with more heart MRIs being conducted finding it and the results of it in studies unrelated to covid (and some related). Mild inflammation will just cause tiredness, no long term damage, as with anything severe cases can cause damage, but you'd be well aware if it by then, chest pains and shortness of breath.
PS; If you are really worried about it, get Astra Zeneca, no issues with clotting in under 30s and not mRNA based.