No it isn't. This line of comments is explicitly in response to your claim:
> Isn't a larger issue the number of immigrants who are NOT contributing to the economy, living at taxpayers' expense
No one has yet mentioned illegal immigrants except you.
In any case it doesn't matter, since GP was specifically replying to:
> In my experience, immigrants have low paying jobs and regularly use cash to avoid paying taxes. Most have no sense whatsoever of cohesion with the country they live in and instead make groups of similar culture that don't really try to fit in.
They were simply giving their own opposite experience on the subject of immigrant wages and taxation, which is equally as valid.
If this thread was actually about illegal immigrants, both comments would be equally off topic. I find it interesting which one you decided to respond to.