At one time, they said that traveling faster than the speed of sound was impossible too.
They just didn’t say it, they gave mathematical proof of it. Einstein never said he was dead on correct. He even thought his theory might have not taken into account everything needed.
Let’s not forget when the choo-choo train was invented that some said the human body couldn’t possibly stand up to the forces it could apply in curves and braking.
That's the same bogus argument made by code toad. Apply logic: Just because someone once made a mistaken negative claim about some physical process does NOT imply that all future negative claims about physical processes are false.
To put it another way. Suppose Fred claims you can't put 1000 marbles in a gallon jar. Then George puts 1000 marbles in a gallon jar. Fred is wrong. Next Bob claims you can't put 1,000,000 marbles in a 5 gallon jar. Though many people try no one comes close to putting a million marbles in the 5 gal jar. Fred's being wrong does NOT imply that Bob is wrong.