Official ban reason (especially the initial one that mentioned "no downsides") does feel out of touch. The main upside is 25% faster pipes, and an argument can be made that the downsides don't compensate enough for it. Hitting a direct pipe on someone is a big deal and often decides the outcome of a fight or a hold. LnL allows demo to do the same but "cheaper", without exposing himself to danger as much. More people have become better with it and started running it full-time at high level, which makes it more apparent that the weapon is an upgrade rather than a sidegrade.
Iron bomber is also an upgrade in almost every scenario, but the difference is that it doesn't really push the demo's upper limit as a class like LnL does. I've never seen anyone say that they'd rather fight a demo with randomly tumbling pipes than IB, because people on both sides prefer a healthier / more consistent gameplay experience with less RNG.
When it comes to stuff like crossbow, gunboats and other straight upgrades, they should evaluated with regards to overall class balance. Before the auto-reloading crossbow, medic was considered to be the most boring and mechanically shallow class, and with it the class feels "in line" with the rest. People had been saying that soldier was the weakest class and scout is the strongest for some time in the past, but the gunboats plugin (a straight buff to soldier) seemed to fix this discrepancy.
I'd say people are more upset about the reasoning rather than the ban itself, and I think it's fair because stuff like that doesn't inspire much confidence in future decision-making process.