Is it acceptable to use proprietary software (platforms) to promote software freedom?

[Adonay Felipe Nogueira]

About this phrase:

"Are there any services we list which don't work with Free Software?"

I would extend it to:

"Does they make the visitor/guest/user use non-free software through
JavaScript?"

If the answer to the above question is "yes", then mark the button with
a special color or symbol, with a nearby note on the issues. No need to
entirely block/remove the button, just mark it specially. I think even
the FSF does this if one clicks the "Syndicate" links in each blog
publication.