I guess I'd like to explain some of the key concerns with non-marine inverter-chargers so that this doesn't seem like a religious issue when it is a real, physical one. And also so that one can reason about it vs treating it as superstition, which it is not.
When passing through shore power, a proper (marine) inverter should maintain neutral and ground entirely separately through the inverter (the bonding between the two is on shore), but the inverter should bond them together when it is inverting and is the source of the AC. So the inverter's transfer switch needs to make and break this bond.
Many non-marine inverters don't do this. Some even do whacky things like form the AC wave by driving both hot and neutral.
This is a real problem because it disables the safety grounding conductor and can let any metal connected to it or the chassis become hot or a current-carrying return path. That includes parts of the boat connected to the water, which means one can put current into the water, among other things.
Another problem that comes up involves the grounding. An inverter has both 12v and 120v in it. For the same amount of work, the current is 10x higher at 12v than 120v, so the wire needs to be much thicker for 12v. Unless the inverter is properly grounded, should something go wrong, DC currents can travel through thin 120v wiring. That is a big fire hazard that often is hard to get right when installing a non-marine inverter.
And, of course, non-marine devices may be more likely to corrode or otherwise fail in the moist, salty, vibration and shock-filled environment of a boat, which is bad -- and makes the problems above worse.
If the inverter is point-of use, without a transfer switch, and in no way connected to the boat's normal AC system, the risks go down a lot. Then the 120v load is just another form of work being done by the boat's DC system, not connecting to, or altering, or reconfiguring, or loading, the boat's or shore's AC wiring in any way. It is basically like a car inverter running a laptop from a cigarette lighter.
I don't want to advocate for anything here. But I do think that one can draw some distinction between a supply and distribution system and a simple load connected to one. Doing that may, or may not, lead one to think about some things differently than if that distinction is not made.