Storming Area 51 is a logistics nightmare. Even reaching it is something that's very difficult, and almost impossible on foot. The nearest civilian rest stop is 86 miles from the base. Even running at 200% capacity it may be able to supply a couple thousand people. As for Area 51 itself, the distance from the gate to the buildings themselves is 28 miles of some of the harshest desert on the planet. You would have to be in peak physical condition (and not the people who signed up to storm the base) just to make it there on foot. The world record for marathon, which is less than the distance that needs to be crossed than the perimeter around Area 51, is just over 2 hours. Imagine doing that in 110 degree heat on blinding white salt flats with no shade. The elements themselves will defeat 90% of the people attempting this stunt, and, given the lack of medical facilities in the area, several thousand will probably die from heat stroke even just camping out in the desert.
Assuming even 10% of the people stupid enough to go manage to cross the desert, Area 51 sits on a US Air Force base. The Air Force has napalm, and they're not afraid to use it, at least in built-up civilian areas in Iraq.
This is Napalm. Water cannot put it out. Yes, they can stop all of you.
Napalm aside, those signs all over the desert warning of the use of lethal force are not jokes. People have been shot, to death, trying to access Area 51. Even if 10% of the keyboard warriors decide not to sleep late and actually storm Area 51, and if 10% of them are surprisingly fit enough to make it the nearly 100 miles through the desert to the base, that means 20,000 people will be on the receiving end of, at the very least, rubber bullets, active denial weapons (which will stop you in your tracks unless you are very stoned on PCP or something), tear gas, and other rather cool non-lethal weapons.
This is Active Denial. It will stop you.
There are also legal ramifications in attempting to storm Area 51, as this Internet lawyer can explain. Even if you are not killed, pelted with rubber bullets, or sent to the hospital for dehydration, you will be sent to jail and fined perhaps half your monthly welfare check.
One can only pray to our Lord Thanos (the best alien, by the way) that at the very least 10% of these idiots do decide to go through with this jackassery so that the universe can become more balanced, as all things should be, through their removal from the gene pool. Best case scenario ALL of them decide to go and balance the universe.
A man can dream, can't he?