...Given the fact that they've been purposefully targeting civilian infrastructure I would say it's pretty clear they have been doing just that...
Targeting of infrastructure does not equate to (nor even reliably hint at) genocide. Sorry.
...You can talk about Hamas using human shields if you want, but it doesn't excuse Israel for then simply choosing to mow down those human shields...
If you are shooting rockets at my family down the block, doing it from your own living room because you're banking on my reluctance to hurt your family, I am well within my rights (and you should not be surprised when I choose) to return fire - no doubt feeling badly about harming your family, but choosing my family's survival over yours. This is not a difficult concept to grasp.
...Regardless of whether they've been deliberately targeting civilians, however, they have killed a large number of civilians...
Ah, so now the case for 'murder of civilians' begins to weaken just a wee bit, eh?
Yes - you and I both new it was going to go this way, before we even began this sequence, didn't we?
The Israelis have, indeed, killed large numbers of civilians during the course of this latest Gaza War.
That is because Hamas war-assets are embedded within their civilian population centers.
Want the large-scale collateral civilian casualties to stop.
Move the war assets away from civilian population centers.
Or suffer continued high levels of civilian collateral casualties.
That is the choice of Hamas - not Israel.
...which at the very least amounts to manslaughter on a massive scale...
Hardly.
It amounts to collateral civilian casualties on a significant scale, incurred during legitimate wartime targeting operations.
The US Army Air Force and the Royal Air Force also inflicted civilian casualties on a significant scale during legitimate wartime targeting operations.
...Though once you reach the number of dead civilians that Israel has racked up I would say it clearly ceases to be manslaughter and turns into murder.
More emotionalism rather than logical and objective analysis.
You have yet to establish 'intentional targeting of civilians', never mind 'murder'.
The scale of the collateral civilian casualties inflicted upon Gazans is directly related to the number of war-assets and war-operations conducted by Hamas in close proximity to their own civilian population centers and to the numbers of civilians in close proximity to any given asset or operation at the time of a given fire-mission.
Much also depends upon the willingness of civilians to temporarily flee the area after receiving preliminary warnings from the Israeli Defense Force.
Murder? Not by any sane definition - legal or ethical or metaphorical - that I've ever encountered.