That simply makes no sense whatsoever, as an argument. If you are against the tyranny of the 51%, you'd be against the tyranny of the 49% (or 45%), no?
The EC does not solve anything in this regard. (The constitution may, by saying that there are certain things that are non-negotiable, no matter if a majority wants them or not--but that's a different matter.)
The only rational argument for the EC would be that states (or localities) are actually important,--rather than just people--and that rural areas, for example, may not get enough power, compared to population centers, because fewer people live there, and that may make it so that the concerns of these areas (which may be different than those of large cities) won't get enough play. (That may be what you meant, but it has nothing to do with the 51%)
However, that really should already be taken care of by the proper division of powers between local, regional, state and federal governments.
When you are electing one person (and their team) for the entire country, I don't think that should play a role at all.--but at least that could be a logical argument.
There is also the fact that it's somewhat outdated, as so many people move around, and why should the power of their vote have anything to do with where they happen to be living at a given time?
The "tyranny of the 51%", while a true concern, is not addressed by the EC whatsoever (as someone else pointed out, you could divide the population into many other arbitrary groupings, rather than location--and say that the majority should not freely govern the minority--are we going to assign electors based on race or sexual orientation, now? Or based on people who prefer Netflix versus Amazon Prime? However you divide up population, there will always be majorities and minorities. Location is not unique in this regard.)
...and in fact "the tyranny of the 51%" is beautifully addressed in parliamentary systems that have a relatively low bar for entry into parliament (5% or less), and in almost all cases the need to build coalitions between multiple parties in order to govern.
Also, another way this problem should usually be addressed, is that, whoever is governing, should govern "for all Americans" and not just the ones that voted for him. Biden at least said that's what he wanted to do, in his speech at Gettysburg. That Trump isn't even pretending to have that intention, is one of the things that makes him so hard to accept for those that are not voting for him.