No, by "dangerous" I mean things that are either directly causing, or could lead to, vulnerabilities in our software system. I'm in the UK. – comment by Ashilta
If you know that there are ways to correct liabilities, write them down, compile them in a list of problems and possible solutions with references to online documents/practices/technologies and present that compilation directly to the manager.
Your intentions seem appropriate, but the more you push your ideas to your workmates while they have no knowledge at all about what you are talking about, it is just natural that they will push you back in a reciprocal way. It is also natural that a department which has successfully accomplished work in the same way for a long period of time resists change.
Instead of justifying what you believe is wrong and right by speaking to them, if you haven't pushed too far already, wait for the manager to read your compilation and let him/her realize that it is in his/her best interest to solve the vulnerabilities you pointed out. He/She may willingly schedule training sessions to the entire team in the practices/technologies that the department chose from your references in order to solve those vulnerabilities.