I have mentioned the way in which the religious try to use the idea of solipsism to introduce uncertainty into the debate over whether the god hypothesis should be taken seriously. I consider their arguments in this regard to be intellectually dishonest because they accept such arguments only when used to support their position--usually by undermining the opposition. If the religious really believed that solipsism should be taken seriously, then they would all call themselves agnostics, because by that reasoning no one knows anything.
If the religious try to take you down the solipsism road, simply point this out to them:
"By your own reasoning you must be an agnostic."
My view is that solipsism itself should never be taken seriously and that the point of considering it is to help ourselves understand how best to approach the world. In other words, the point of solipsism isn't that we can never really know anything, which is what many people seem to think it implies, but that we must take care when defining what we mean by terms such as "knowledge" and "evidence".
There is a second point to be learned from a consideration of solipsism: Keep an open mind regarding any new evidence that may come along, but that doesn't mean you can't reach any conclusions based on evidence you have before you. The question is: "What degree of certainty should you require before reaching a conclusion?"
Should the remote possibility that Harry Potter, Merlin, or some other wizard has bewitched you into thinking that something is real prevent you from concluding that the thing is real? Of course not. It is always possible that there is some hidden bit of information that may change your view on something. If you have sufficient information for your purposes, however, you should go ahead and make up your mind.
To illustrate, in contract law are notions of conditions that apply to a party's duty to fulfill his part of a contract. One major distinction between types of conditions is that between conditions precedent and conditions subsequent. A condition precedent, as the name implies, must be met before the party has a duty to fulfill his part of the contract. A condition subsequent will be fulfilled, if at all, after the duty to perform under the contract arises.
If the contract calls for delivery of goods before the buyer has to pay, then delivery is a condition precedent upon the buyer's duty to pay. If the contract provides that after the purchase is completed the buyer may return the goods within a certain time period if not satisfied, that is a condition subsequent. The condition subsequent does not relieve the buyer of the duty to pay for the goods, rather it provides for changes to the duties of the parties after that fact. Depending on the terms of the contract, the seller may be allowed to attempt to remedy any defects in the goods before refunding any money. The contract could call for a partial refund or total refund, etc.
Likewise the possibility that there is something you don't know about the universe (or maybe couldn't even have guessed), if sufficiently remote, is merely a reminder to keep an open mind. Should such unforeseen things turn out to be true, then and only then, should you adjust your conclusion.
The religious like to take solipsism seriously because it not only allows them to argue for the respectability of their delusion, it also reflects their own mind set--their lack of self-confidence in their own intellect. (I know I compare religion to narcissism and this self-doubt may seem to contradict that, but in actuality, pathological narcissism is rooted in an extreme lack of confidence that the sufferer is trying to mask.) This lack of self-confidence helps explain why the religious think it is convincing to argue that "a lot of people believe". That is the way they think: They don't trust their own judgment and they are too insecure to live with criticism for not conforming.
But, that is all a tangent to help us understand what the religious mind is like. What is more important to the main question is the realization that the god hypothesis IS solipsism. Solipsism taken completely seriously, taken as a world view--indeed a universal view. Religion is the belief that our reality is not reality but some sort of temporary, temporal trial to be followed by an eternity in a place that is real in some absolute sense.
This is another reason agnostics should not let themselves be bullied into taking solipsism seriously (and thus should not be agnostic): Because it is logically almost indistinguishable from being a believer. Both viewpoints take the possibility of a "greater" reality seriously without any evidence to support it.