I think I expressed myself poorly, the certificate is not ignored in the implementation, only the verification of validity will be ignored. All trasações still being with encryption SSL or TLS
SSL or TLS is nearly useless without validation checks. This would be a severe security flaw, please don’t use that! Just imagine that some of your people use a free WiFi to connect to your server. The WiFi admins can do a MITM attack with one click and all .gov.br data would belong to them.
To see which severy security problems are caused by not validating certificates, please read http://www.search-lab.hu/about-us/news/109-security-vulnerability-in-lg-s-update-center-application (for instance).
DAVdroid would rather need a good certificate pinning option, but ignoring the certificate is not a possible option.