Actually, the Antikythera find was subject of much discussion.  What it actually turned out to be (an advanced astronomical calculator) was what it was believed to be early on.  Scientists didn't dismiss it, what they did dismiss were the "theories" that it was proof of Atlantis, or ancient astronauts, or whatever.

As for continental drift, as a geologist I have to speak up.  Wegener made his proposal based on evidence everyone agreed with.  It wasn't dismissed at the time because scientists were hidebound, but because his proposed mechanism was quickly shown to be highly unlikely.  What people who use this example either don't know or overlook was that there was a host of competing theories to try and explain the same data, and Wegener's theory simply didn't have any more evidence, at the time, than they did.

Fast forward a few decades, with more data collected and, most importantly, discovery of the mid ocean ridges, the various trenches, the ability to map the magnetic field of the sea floor, and now Wegener's idea now had a mechanism.  With the evidence and, most importantly, an explanation as to how it could happen, pretty much the entire geological community accepted it overnight.

As to the LHC, as has been pointed out, repeatedly, the energy involved int he particle collisions is many times smaller than that created in the atmosphere by high energy cosmic rays all the time.  In other words, nothing that's going to be done at the LHC doesn't already happen routinely in nature.  The only difference is that doing it at the LHC means doing it where the results can be observed and measured