Here's a question for y'all: would you wheel your cassette into a motorway services toilets and empty it in there? I have. Not out of habit, just occasionally when it needs emptying. My take on it is that very few people in there would know what it is, and so long as it is clean on the outside they might just assume it is some kind of tool box.
So if folk don't know what it is that makes it ok.
I have witnessed folk doing this in various places and the mess they leave is disgraceful.
In New England Bay it got so bad that the public toilets were unfit for human use, and were closed. Dumfries and Galloway Council had to instal an Elsan point
Even on Arran where two free Elsan points have been installed the toilets in Brodick is used like this, even though there is a sign telling you where the Elsan points are, and asking you not to do this, and the toilets are covered in blue and green.
They normally scuttle in and out in about a minute when its dark or getting dark, hoping that no one can see them.
Wonder why, even when signs are up asking them not to do it.
Remarkably they claim to have left the toilet cleaner than when they entered.
Now here's an idea, when planning a trip make sure you plan it in such a way you will have access to an Elsan point as required.
It's not that difficult, in nine years I have never emptied my cassette into a public toilet.
But I have witnessed many times the results of those that do.
So to answer your question, no I would not.