Is it is bad for bees? I have a mulberry that gets this every year. Its gross lol. I am putting in bee hives and would like to know if this stuff would harm them.

No harm to any non-target organisms at all, including bees and other pollinators.

btw, all this is easily researched online.

Sultry, no they don't harm the bees if it did I wouldn't use it since I keep bees.

Cardinals nearly always present here; do you suppose that they would go for tent worms?

The cardinals spend a good deal of time repeatedly flying/jumping up from window sill (alternatively flying from adjacent tree) to pane divider, picking off probably ants, one per flight/jump.

You bet!! Birds are a great defense against tent caterpillars!

Cardinals probably would. Mine don't they are more interested in the mulberries. Usually my wasps take care of them especially if I break up the webs a little bit with a stick but this year I had way to many worms for the wasps to handle and had to intervene

I have the vague notion that bee keeping is labor intensive; but perhaps it also can be done in a laissez faire way if honey producton is not an objective?

I am guessing that (sub)urban municipalities probably prohibit it.

I find these web worms are not a problem. They typically defoliate towards the end of summer when the plants have already gotten most use out of their leaves and fall is coming soon. I’m sure this is no accident of nature. Every plant they have defoliated always comes back fine for me.

Sultry you are completely right. That is exactly how it is with bee keeping.