Ultimately, no politician can please everyone. Each of them make mistakes, some more painful than others. And only some of them make notable achievements. If a politician does no wrong but also nothing notably good, they fade into obscurity.
A lot of the hate rhetoric for Thatcher seems centered around British policies in dealings with the other territories, namely Scotland and Ireland. It took a very long time to stabilize things and along the way, there were people seriously upset on all sides. Nobody likes to compromise. And when looking at things in retrospect, there's always a perceived better way to have handled them. Did her policies help pave the way towards eventual stability? Or were there many corrections necessary to "undo" what she'd done?
What's most difficult to know is if policies that make things more uncomfortable for a period of time are a necessary step towards eventually making improvements. There always has to be sacrifice made somewhere. It must take extremely skilled and thoughtful analysts to comb through all the data and make objective assessments as to the cause and effects of policies, determining what worked well and what didn't.
But then you have people who have made up their mind on how they see things and will select choice bits here and there to support their view, ignoring anything else that may contradict it.
Take the sinking of the General Belgrano. It was outside the zone of exclusion by just over 30 miles when attacked. But if you look at the maps of their course, it was mostly straight along the southern perimeter, until the last few hours before it sunk. It was switch backing, approaching the zone, then moving away from it, then approaching again. It looked like it was "daring" to enter the zone, heading for it and then veering off, only to repeat it again. There didn't appear to be any good reason for it be on such a course other than to antagonize the British. But given the stealth and speed of the HMS Conqueror (the sub that sunk the Belgrano), wouldn't one torpedo have been enough? Partially damage the ship and let it limp back home? Or was the order to sink it outright?
So Thatcher gets a call from the Royal Navy, saying how there's this Argentinian destroyer testing the exclusion zone southern boundary and that there's concern on what it might do next. She was probably advised that the prudent thing to do is treat the vessel as having violated the spirit of the exclusion zone. Was she a war monger? I highly doubt it. It was regrettable that over 300 crew members died, but thankfully far more were rescued. If she was really so vicious, she would have ordered the ship's destruction with orders for there to be no survivors. Clearly, this was not the case. But, for anyone hating Thatcher, it's easy to twist it around and make it look like she was viciously insensitive.
I do sometimes wonder if she was as uncompromising as she was to compensate for her being the first female PM. Was she a more approachable and warm person off camera? I wonder if we'll ever get to see or hear informal recordings of her personal interactions with other politicians made off mainstream camera. It would certainly give us more insight into her character.