I have never understood the rejection of walls as an effective means of preventing access. Ladders, tunnels, battering rams, and 'going around' have all existed for millenia, but we've kept on building walls the whole time. How could the whole world be deluded about that for so long?

If you enter your bank password over unsecured public wifi, someone there could steal it. But my advice to someone who does banking in a wifi cafe would not be "don't use a password at all, it does nothing for you".

Or am I missing something?

All banks use HTTPS so there is no real risk that someone will steal your password over unsecured wifi.

Border walls can only prevent access if there are actual guards and sensors monitoring the wall and responding when people attempt to go over, under, or through. That would be extremely expensive. Is it a good use of public funds?

What's the alternative, give up on border control? How fair is it that people from India wait 20 years for a green card for following the rules while others just walk across illegally?

I don't understand the seeming position by some on the left that there's no need for border security.

I'm not opposed to border security. I just don't think that building a wall would be a cost effective means of achieving that goal. Plus there would be some negative environmental impacts.

It depends on the location and if it's combined with other things. An unmonitored wall would add little by itself.

In some places there already exist walls and they do help.

Properly manned physical barriers work - see the San Diego / Tijuana fence

undocumented immigrants used to just walk across, and have now switched to the mountains/deserts and to a lesser extent the ocean