This is true in abstract but most of these claims have details which can be tested. You can’t disprove a perfect conspiracy but you can show that the named people don’t exist or weren’t in the place at that time, the “proof” image has incorrect details (e.g. remember the birthers alleging Obama had a birth certificate which mixed the name and seal of different countries and time periods?).

If it has enough detail to be tested, you can more justifiably mark it as fake. The vague unfalsifiable stuff is much less satisfying for people to spread.