False, without HTTPS content can be intercepted and modified, and this happens all the time.
My ISP is blocking sites by displaying Ads, a little research revealed that ISP is doing it. The source of that advert contains my ISP’s name in it.
Time Warner Cable is inappropriately injecting ads into various web sites via its TWCWiFi hotspots.
Telkomsel (ISP) is injecting ads onto sites.
AT&T hotspots are tampering with HTTP traffic and injecting ads.
Comcast Injecting ads “injecting this into every non-https website i visit is really, really, really, really pissing me off”