Well done in finding URL's to support your thesis. However they are a mixture of the untrue the exaggerated and the plain foolish.First the untrue.
"Some of them -- Java applets in particular -- can carry viruses that can infect your computer in a variety of harmful ways"
Java applets execute in a "Sandbox" which prevents them writing to your local file system without explicitly and obviously asking to do so first. There has been no recorded I emphasise NO recorded incident of virus infection from a standard Java applet
I'd be interested to hear of comments on Flash and security, which by the way I have not heard anything bad about in relation to security.
"The Java concurrency architecture is based on threads, which encourage the creation of delicate software systems that are vulnerable to sudden and catastrophic lock-up after deployment because of undetectable deadlock bugs"
There is no connetion between Threading and "delicate software systems that are vulnerable and catastrophic lock-ups", a passing knowledge of software development would indicate this is a confused, confusing and bizzare view of technology. Modern operating systems include Threading technology, modern programming languages include threading technologies.
"Its no secret that supposedly portable Java clients do not run the same on all platforms. For one thing, the byte stream and memory handling are different for Microsoft Windows, Apple Macintosh and Unix. If developers know what theyre writing for, its easier to make Java work. But the one-size-fits-all claims are bogus."
Now here we come to a hint of truth. Microsoft created what one of its executives called a "polluted" version of Java that broke some of the compatibility goals of Java. As a result of legal action they have been restrained from doing this. The current standard Java plugin offers the most binary portable execution environment ever. This means the same binary will run unmodified on Windows/Linux/Unix/Macintosh. That is not to say that it is not possible to find some combination of hardware and operating system that will have issues, it is certainly possible to find such a combination. In the same way it is possible to find some combination of Windows/Hardware/Patching that will cause a standard windows program to have problems.
"Java is fairly rough on system resources and can cause some browsers to lock up when viewing a web page. It is a good idea to limit the use of java applets in general -- remembering that there still is a good number of users out there with older versions of internet software. http://www.rootsweb.com/rootsweb/wizards/webmasters.html"
Again I agree with this, use applets where you are likely to benefit from their abilities. If you browse sites with applets on a machine with 64 MB of RAM you may well get poor performance.
"You might attempt to run the applets and your browser would freeze and lock-up your operating system with some damnable memory over-write which could generate a severe I/O error. http://www.cubethis.com/java.htm"
I do wish people would write about subjects they actually know about. If you visit a page with a large applet you may get a long delay as it is downloaded. You will not get a memory over write, you will not get an I/O error, why? Because Java does not include the ability to write to arbitrary memory addresses, it does not have the ability to write to your file system. It is possible that a faulty JVM falls over, but that is like blaming HTML as the problem if your browser cannot render it.